---------------------------------------------------------------
      ---------------------------------------------------------------
             A      RRRR     I  TTTTTTTTT  V       V  EEEEEE
            A A     R   R    I      T       V     V   E     
           A   A    RRRR     I      T        V   V    EEE   
          AAAAAAA   R   R    I      T         V V     E     
         A       A  R    R   I      T          V      EEEEEE 2K
      ---------------------------------------------------------------
      ---------------------------------------------------------------



                           USER'S GUIDE 

                           Le Mans, first version: 1984
                           Last update: January 2000, 
                               all previous 4 programs gathered in one,
                               greatly simplifying the use.

                           A. Le Bail
                           Universite du Maine
                           Laboratoire des Fluorures
                           ESA CNRS 6010
                           Avenue O. Messiaen
                           72085 Le Mans Cedex 9
                           FRANCE 

                           E-mail :
                          either   armel@fluo.univ-lemans.fr
                              or   alb@cristal.org
                              or   cristal@cybercable.tm.fr
                              or   lebail@univ-lemans.fr
   -----------------------------------------------------------------
   -----------------------------------------------------------------


                         SHORT INTRODUCTION:


                              ARITVE is
   a program for modelling amorphous structures by a Rietveld-type
   refinement of the atomic coordinates and cell parameters taken
   from a starting crystalline model. The data fitted are the S(2t) 
   interference functions (see § A). Up to three S functions can
   be simulated simultaneously, either neutron or X-ray data or both
   together with different wavelengths. The imaginary part of the
   X-ray diffusion factors is correctly treated (I hope). A non-zero
   S(0) cannot be reproduced.
   From the crystalline model, a powder diffraction pattern is
   generated by the summation of all contributing reflections (hkl)
   with a Gaussian profile shape. The FWHM (Full Width at Half Maximum)
   angular dependence may follow a microstrain-type description 
   (variation as tan(theta)), but the instrumental resolution and 
   eventually a size effect are simply taken into account by a 
   Cagliotti-type expression.
   Not every model will give a "good" fit by using this method. Only
   "good" model(s) will give "good" fit(s). An eventually "good" model
   may be soon detected : low Rp (Reliability on profile, according to
   the Rietveld original definition) is obtained BEFORE refinement.
   It is recommended not to try models inconsistent with already known
   structural aspects (distances, coordinations, density...).

   ARITVE can only improve (by refinement) a yet "good" model. 

   Test files are provided that correspond to the fit of glassy SiO2
   neutron and X-ray data published in :
   "Modelling the silica glass structure by the Rietveld method,"
   A. Le Bail, J. Non-Cryst. Solids, in press (1995).
   However, the fit does not correspond to the final result in the
   P212121 space group but to an intermediate result with higher
   symmetry (P213). 

                         Note that ARITVE is not
   a convivial program easy to manipulate. Do not expect to get a
   result before some weeks on your own problem although you may
   install and apply the program on the test data in a few minutes.

   Some french text may have been forgotten somewhere. This package
   has not been extensively tested by many users, bugs are possible.

   -----------------------------------------------------------------
   -----------------------------------------------------------------

                              CONTENT

  A- How to run the program: definitions of files and parameters
  
  B- Strategy
   B-1- The model
   B-2- An order to respect for parameter refinement

  C- What can be expected from ARITVE

  D- How ARITVE could be eventually improved

  E- Final recommendations

  F- BIBLIOGRAPHY - REFERENCES

  G- LIST OF CAUSES OF MAJOR PROBLEMS

   -----------------------------------------------------------------
   -----------------------------------------------------------------

   A- How to run the program: definitions of files and parameters

      Explanations are given corresponding to the example of the
      test files:

      ARCAR.DAT   data file with commands for structure refinement
      ASIO2N.NOR  neutron interference function of SiO2
      ASIO2X.NOR  X-ray interference function of SiO2

      ARITVE.ZIP contains also : 
           ARITVE.EXE   : the axecutable for Windows 95/NT/98
           ARITVE.F     : the Fortran source code
           LICENSE.HTML : the GNU General Public License
           ARITVE.TXT   : this manual

      I the general case, one .dat file with instructions will be
      needed as well as up to 3 .nor files containing interference
      functions.

       The data included in the SiO2 .NOR files are from:
         J.H. KONNERT & J. KARLE, Acta Cryst. A29, 702 (1973)
              for X-rays
       and P.A.V. JOHNSON, A.C. WRIGHT & R.N. SINCLAIR, J. 
           Non-Cryst. Solids, 58, 109 (1983).
              for neutrons

       The starting model is that of the Carnegieite structure:
          F.W. BARTH & E. POSNJAK, Z. fur Kristallogr. 8, 376-385 (1932).
       But the starting coordinates and cell parameters are from
       the (may be false) description of a high-cristoballite form
       with the carnegieite model:
          T.F.W BARTH, American Journal of Science, Serie 5,
                        23, 350-356 (1932).
       (see also Wyckoff, Crystal Structures, Volume I).


       WARNING : These "interference functions" are the so called

                                S(2t) 

                      i.e. the equivalent of

                                S(Q)

                  with a contant 2*theta step (the diffracted
                  intensity, properly corrected, divided by
                  <f**2>). Here, the test files are given at
                  an arbitrary scale (multiplied by an
                  arbitrary constant).


       ASIO2N.NOR  is given there, the first line must contain three
                   values :

                   nbmes 2t Step           unformatted

                   nbmes     =   number of intensity data
                   2t        =   starting two theta angle
                   Step      =   constant step in two theta degrees


                   Then the nbmes intensities are given (unformatted)      


       230  0.00  0.40
   0.00000E+00   0.65620E+03   0.68291E+03   0.73245E+03   0.80835E+03
   0.93140E+03   0.11210E+04   0.13651E+04   0.16390E+04   0.19135E+04
   ......
   0.57189E+04   0.57198E+04   0.57212E+04   0.57232E+04   0.57258E+04
   0.57290E+04   0.57327E+04   0.57370E+04   0.57418E+04   0.57474E+04
   0.57535E+04   0.57602E+04   0.57674E+04   0.57753E+04



  The same for ASIO2X.NOR :


  230 0. 0.4
     0.     93.    232.    421.    639.    833.   1042.   1255.   1461.   1674.
  1890.   2106.   2321.   2558.   2800.   3054.   3368.   3760.   4287.   4959.
  5787.   6738.   7703.   8556.   9142.   9386.   9251.   8808.   8203.   7549.
   ......
  5195.   5195.   5202.   5215.   5230.   5254.   5296.   5350.   5401.   5469.
  5538.   5620.   5694.   5793.   5890.   5984.   6059.   6133.   6206.   6268.
  6335.   6398.   6457.   6500.   6542.   6566.   6578.   6589.   6596.   6583.





      the ARITVE program is started by

      ARITVE
      entry file (no extension)?? ARCAR
 



      The .DAT file must be prepared as follows:


    The test file ARCAR.DAT:

line  !  CONTENT

 1.   !  IF AMORPHOUS SiO2 WAS TYPE CARNEGIEITE P213
 2.   !  90 2 13 1 0 0 0 0 0 0
 3.   !  SiO2-N
 3.   !  SiO2-X
 4.   !  1 4
 5.   !  4 2
 6.   !  0.5000 0.7093
 7.   !  0.5 0.8 0.8 0.05
 8.   !  P 21 3
 9.1  !  0.4149 0.5803
 9.1  !  0.0704 0.0060
 9.2  !  6.2915 2.4386 3.0353 32.3337 1.9891 0.6785 1.5410
          81.6937 1.1407 0.0817
 9.2  !  3.0485 13.2771 2.2868 5.7011 1.5463 0.3239 0.867
          32.9089 0.2508 0.0106
 10.1 !  SI1 
 10.2 !   1  0.25500  0.25500  0.25550  0.04000
 10.1 !  SI2 
 10.2 !   1 -0.00800 -0.00800 -0.00800  0.04000
 10.1 !  O1  
 10.2 !   2  0.12500  0.12500  0.12500  0.04000
 10.1 !  O2  
 10.2 !   2  0.66000  0.66000  0.06200  0.12000
 11.  !      60.97914    313235.4      5000.0    106958.6
 11.  !      48.11535    566242.9     10000.0    279894.0
 12.  !   7.16000     7.16000     7.16000    90.00000    90.00000    90.00000
 13.1 !   2
 13.2 !   0 440
 13.2 !   9200 17500
 13.1 !   2
 13.2 !   0 600
 13.2 !   9200 17500
 14.  !   1.0
 14.  !   1.0
 15.  !   asio2n.nor
 15.  !   asio2x.nor
 16.  !   81 81 81 0
 16.  !   91 91 91 0
 16.  !   101 101 101 0
 16.  !   111 121 131 0
 17.  !   11
 17.  !   21
 18.  !   31 0 41
 18.  !   51 0 61
 19.  !   71 71 71 0 0 0




               -----------------------------------------------
               | -------------------------------------------  |
               | |        PARAMETER  DEFINITIONS           |  |
               | -------------------------------------------  |
               ------------------------------------------------
   

  LINE  1 :   TEXT         --> TITLE                FORMAT 20A4
  ---------

  LINE  2 :   NCYCLE,NPAT,MAXS,LG,IF1 to IF6        FREE FORMAT
  ---------
          NCYCLE   -->      NUMBER OF REFINEMENT CYCLES
          NPAT     -->      NUMBER OF PATTERNS (MAXIMUM 3)
          MAXS     -->      NUMBER OF REFINED PARAMETERS
          LG       -->      CODE TO SEE EVENTUALLY Iobs AND Icalc
                            ON THE SCREEN: IF 0 --> YOU SEE THEM
                                           IF 1 --> YOU DO NOT
                            INTEREST :  ESTIMATE THE SCALE FACTOR
                                        WHEN THE REFINEMENT IS STARTING
                                        AND ALSO THE FWHM PARAMETERS
          IF1 to IF6  -->   Codes for optional output files
                            IFn=0  no output
                            IFn=1  output
                 IF1  :  *.out file, contains contributing hkl to each point
                 IF2  :  bidon.hkl, the list of hkl and multiplicity
                 IF3  :  *.pre, intermediate file before refinement
                 IF4  :  bidon.imp, intermediate file
                 IF5  :  bidon2.imp, intermediate file
                 IF6  :  *.lt4 contains observed and calculated data

   LINE  3 :      PTEXT    -->  ONE TITLE FOR EACH PATTERN  FORMAT 4A4
   ---------
                   =====> NPAT LINES (max NPAT = 3)

   LINE  4 :      KXR(1)  KXR(2) KXR(NPAT)             FREE FORMAT
   --------- 
                   =====> NPAT VALUES ON ONE LINE

                   KXR -->  CODE FOR THE PATTERN TYPE:
                          1 :  NEUTRONS
                          4 :  X-RAYS

   LINE  5 : NA,KL                                     FREE FORMAT
   ---------
                 STRUCTURE INDICATORS :

              NA     --> THE NUMBER OF INDEPENDENT ATOMS CONTAINED 
                         IN THE ASYMMETRIC UNIT (Max = 50)
              KL     --> THE NUMBER OF ATOMS HAVING DIFFERENT
                         DIFFUSION FACTOR, EITHER NEUTRONS OR X-RAYS
                         (Max = 4)
  
     LINE  6 :    DLABDA(1) .... DLABDA(NPAT)          FREE FORMAT
     ---------
                  WAVELENGTHS IN ANGSTROMS FOR EACH PATTERN

                  NPAT VALUES ON ONE LINE


     LINE  7 :     RELAXC,RELAXB,RELAXS,RELAXH  
     ---------
                   RELAXATION FACTORS APPLIED BY MULTIPLICATION
                   ON THE SHIFTS AFTER EACH REFINEMENT CYCLE

                RELAXC --> CONCERNS ATOMIC COORDINATES
                RELAXB --> UNUSED
                RELAXS --> CONCERNS SCALE FACTORS AND OCCUPANCY FACTORS
                RELAXH --> CONCERNS CELL PARAMETERS AND FWHM


    LINE  8. :    Space group
    ----------
        Spacegroups are defined as in Lazy-Pulverix :                                                                     
        KLAUS YVON, WOLFGANG JEITSCHKO  AND  ERWIN PARTHE            
                              J.APPL.CRYST. (1977), 10, P 73-74 
                                                                                                                                         
 S P A C E  G R O U P  SYMBOLS  
                                                                     
                                                                     
    DO  N O T INCLUDE THE STAR  PRECEEDING SOME OF THE SYMBOLS.      
    THE STAR INDICATES CENTROSYMMETRIC SPACE GROUPS WHICH HAVE       
    BEEN DESCRIBED WITH SEVERAL SETTINGS. THE PROGRAM GENERATES    
    ONLY THE SETTING WITH THE CENTRE OF SYMMETRY AT THE ORIGIN OF    
    THE UNIT CELL.                                                   
                                                                     
                                                                     
   W A R N I N G     A SYMBOL THAT DOES NOT FIGURE IN THIS LIST      
                       MAY YIELD WRONG EQUIPOINTS.                   
                                                                     
   TRICLINIC                                                         
    P 1          P -1                                                
                                                                     
                                                                     
   MONOCLINIC                                                        
    P 2          P 21         C 2          P M          P C          
    C M          C C          P 2/M        P 21/M       C 2/M        
    P 2/C        P 21/C       P 21/N       C 2/C                                  
                                                                     
    THE POINT POSITIONS GENERATED FROM THESE SYMBOLS CORRESPOND TO   
    THE MONOCLINIC SETTING WITH B AS UNIQUE AXIS (ALPHA=GAMMA=90.)   
                                                                     
   ORTHORHOMBIC                                                      
    P 2 2 2      P 2 2 21     P 21 21 2    P 21 21 21   C 2 2 21     
    C 2 2 2      F 2 2 2      I 2 2 2      I 21 21 21   P M M 2      
    P M C 21     P C C 2      P M A 2      P C A 21     P N C 2      
    P M N 21     P B A 2      P N A 21     P N N 2      C M M 2      
    C M C 21     C C C 2      A M M 2      A B M 2      A M A 2      
    A B A 2      F M M 2      F D D 2      I M M 2      I B A 2      
    I M A 2      P M M M     *P N N N      P C C M     *P B A N      
    P M M A      P N N A      P M N A      P C C A      P B A M      
    P C C N      P B C M      P N N M     *P M M N      P B C N      
    P B C A      P N M A      C M C M      C M C A      C M M M      
    C C C M      C M M A     *C C C A      F M M M     *F D D D      
    I M M M      I B A M      I B C A      I M M A                   
                                                                     
                                                                     
   TETRAGONAL                                                        
    P 4          P 41         P 42         P 43         I 4          
    I 41         P -4         I -4         P 4/M        P 42/M       
   *P 4/N       *P 42/N       I 4/M       *I 41/A       P 4 2 2      
    P 4 21 2     P 41 2 2     P 41 21 2    P 42 2 2     P 42 21 2    
    P 43 2 2     P 43 21 2    I 4 2 2      I 41 2 2     P 4 M M      
    P 4 B M      P 42 C M     P 42 N M     P 4 C C      P 4 N C      
    P 42 M C     P 42 B C     I 4 M M      I 4 C M      I 41 M D     
    I 41 C D     P -4 2 M     P -4 2 C     P -4 21 M    P -4 21 C    
    I -4 M 2     P -4 C 2     P -4 B 2     P -4 N 2     P -4 M 2     
    I -4 C 2     P -4 2 M     I -4 2 D     P 4/M M M    P 4/M C C    
   *P 4/N B M   *P 4/N N C    P 4/M B M    P 4/M N C   *P 4/N M M    
   *P 4/N C C    P 42/M M C   P 42/M C M  *P 42/N B C  *P 42/N N M   
    P 42/M B C   P 42/M N M  *P 42/N M C  *P 42/N C M   I 4/M M M    
    I 4/M C M   *I 41/A M D  *I 41/A C D                             
                                                                     
                                                                     
   TRIGONAL                                                          
    P 3          P 31         P 32         R 3          P -3         
    R -3         P 3 1 2      P 3 2 1      P 31 1 2     P 31 2 1     
    P 32 1 2     P 32 2 1     R 3 2        P 3 M 1      P 3 1 M      
    P 3 C 1      P 3 1 C      R 3 M        R 3 C        P -3 1 M     
    P -3 1 C     P -3 M 1     P -3 C 1     R -3 M       R -3 C       
                                                                     
    ALL R-SPACE GROUPS REFER TO THE HEXAGONAL SETTING                
                                                                     
   HEXAGONAL                                                         
    P 6          P 61         P 65         P 62         P 64         
    P 63         P -6         P 6/M        P 63/M       P 6 2 2      
    P 61 2 2     P 65 2 2     P 62 2 2     P 64 2 2     P 63 2 2     
    P 6 M M      P 6 C C      P 63 C M     P 63 M C     P -6 M 2     
    P -6 C 2     P -6 2 M     P -6 2 C     P 6/M M M    P 6/M C C    
    P 63/M C M   P 63/M M C                                          
                                                                     
                                                                     
   CUBIC                                                             
    P 2 3        F 2 3        I 2 3        P 21 3       I 21 3       
    P M 3       *P N 3        F M 3       *F D 3        I M 3        
    P A 3        I A 3        P 4 3 2      P 42 3 2     F 4 3 2      
    F 41 3 2     I 4 3 2      P 43 3 2     P 41 3 2     I 41 3 2     
    P -4 3 M     F -4 3 M     I -4 3 M     P -4 3 N     F -4 3 C     
    I -4 3 D     P M 3 M     *P N 3 N      P M 3 N     *P N 3 M      
    F M 3 M      F M 3 C     *F D 3 M     *F D 3 C      I M 3 M      
    I A 3 D                                                          
                                                                     


    LINE  9.1 :  KL VALUES (SEE LINE 5) OF
    ----------          - FERMI LENGTHS - NEUTRON CASE
                 OR OF  - DELTA F"      - X-RAY CASE
                          (IMAGINARY DISPERSION CORRECTION)

                 FOR EACH PATTERN (NPAT LINES)

                   FREE FORMAT 

                 THE ORDER OF THE KL VALUES MUST BE CONSISTENT
                 WITH THAT GIVEN LATER

                 WHEN THE PATTERN IS A X-RAY PATTERN, A 9.2 LINE
                 MUST FOLLOW


    LINE  9.2 :  A1 B1 A2 B2 A3 B3 A4 B4 C DELTAF'       FREE FORMAT
    -----------
                 
                 9 COEFFICIENTS FOR ANALYTICAL APPROXIMATION TO THE X-RAY
                 SCATTERING FACTORS FOLLOWED BY THE REAL PART OF THE
                 DISPERSION CORRECTION
 
                  --------------------------------------------
                   LINES 10.1 AND 10.2  :: ATOMIC PARAMETERS 
                  --------------------------------------------
  
                   TO BE GIVEN NA-TIME (SEE LINE 5)

     LINE 10.1 :   IDENTIFICATION ASCII FOR THE N-IEME ATOM
     ------------   
                    FORMAT A4

     LINE 10.2 :   NTYP,X,Y,Z,NOCCUP
     ------------
                    FREE FORMAT

                    NTYP --> ORDER NUMBER OF THE CORRESPONDING DIFFUSION FACTOR
                    X,Y,Z --> REDUCED ATOMIC COORDINATES
                    NOCCUP --> SITE OCCUPANCY
                               ALL VALUES CAN BE MULTIPLIED BY A CONSTANT,
                               THIS CAN BE TUNED ALSO BY THE SCALE FACTOR.

     LINE 11. : SCALE U V W              FREE FORMAT
     -----------
             ===>  FOUR VALUES FOR EACH PATTERN

                SCALE --> SCALE FACTOR
                U     --> LINE-WIDTH FACTOR
                V     --> LINE-WIDTH FACTOR
                W     --> LINE-WIDTH FACTOR
 
            FWHM == SQRT(U*Tg**2(theta) + V*Tg(theta) + W)
                and the FWHM is the full width at half maximum in 
                (2-theta degrees)*100

     LINE  12. : A,B,C,ALPHA,BETA,GAMMA      FREE FORMAT
     -----------
                   DIRECT CELL PARAMETERS

  npat groups of lines 13.

     LINE 13.1 : Nex   = number of excluded zones       Free Format
     -----------         for the nth pattern

     LINE 13.2 : ilow, ihigh                            Free Format
     -----------          = the low and high limits
                          of the excluded zone
                          in degrees 2*theta*100
                  Nex lines 13.2 have to be given
                  If Nex=0 for the nth pattern, give no 13.2 line

  Then, npat groups of lines 14. have to be given

     LINE 14.  : Iscale                        Free Format
     ----------- Iscale = a multiplicative factor 
                            used to eventually modify
                            the intensities of the nth
                            interference function.
  npat groups of line 15.

     LINE 15.  : name.nor                     20A1
     -----------     = name of the nth datafile


     LINES 16 TO 19 : CODES TELLING THE PROGRAM TO REFINE OR NOT THE PARAMETERS 
     --------------------------------------------------------------------------
                  APPEARING IN THE SAME ORDER AS THE PARAMETERS LINES
                  10.2, 11 AND 12


                  THE KEY OF THESE CODES IS GIVEN HERE:

                  CODE = [ M * 10 + ABS(SM) ] * SIGN(SM)

                     WHERE : M --> M-IEME REFINED PARAMETER
                            SM --> MULTIPLYING FACTOR APPLIED TO THE SHIFT
                                   FOUND FOR THE M-IEME PARAMETER AT EACH
                                   REFINEMENT CYCLE
                 EXAMPLES :

                       IF  CODE = 101     , this is the
                                  10th PARAMETER, THE SHIFT WILL
                                     BE MULTIPLIED BY +1
                       IF  CODE = 100.5   , this is the
                                  10th PARAMETER, THE SHIFT WILL
                                     BE MULTIPLIED BY +0.5
                       IF  CODE = 0
                                  THIS PARAMETER IS NOT REFINED
        
                IT IS POSSIBLE TO ASSOCIATE SOME PARAMETERS IN A SIMPLE 
                WAY:
                FOR INSTANCE         X, Y=1/2+X, Z
                THE CODES FOR X AND Y SHOULD BE THE SAME BECAUSE
                    THE SHIFTS ON X AND Y=1/2+X WILL BE THE SAME :
                                    101 101 111

                FOR INSTANCE         X, Y=-X, Z
                THE CODES FOR X AND Y COULD BE 101 AND -101
                                    

                OTHER EXAMPLE:       X, Y=2X, Z
                THE CODES FOR X AND Y COULD BE 100.5 AND 101.
                                       OR      101.  AND 102.
                       BECAUSE THE SHIFT ON Y IS TWICE THAT ON X
      

                THE ORDER FOR THE NUMBER OF THE PARAMETERS IS 
                UNIMPORTANT. iT IS JUST RECOMMENDED THAT THE MAXIMUM
                NUMBER IS EQUAL TO MAXS (LINE 2)


                FORMAT ALWAYS FREE FOR THE CODES


     LINE  16.  : FOUR CODES POUR X,Y,Z,NOCCUP           FREE FORMAT
     ----------
                  NA LINES TO BE GIVEN (put always the NOCCUP code = 0)

     LINE  17. : ONE CODE FOR SCALE FACTOR               FREE FORMAT
     ----------                 
                  =====>  NPAT LINES

     LINE  18. : THREE CODES FOR U, V, W                 FREE FORMAT
     ----------                 
                  =====>  NPAT LINES

     LINE 19 : 6 CODES FOR THE CELL PARAMETERS          FREE FORMAT
     ----------

                  ============>>>>>>>> ATTENTION
                              THESE CODES APPLY TO A RECIPROCAL
                              METRIC TENSOR
                 THE CONSTRAINTS WHICH SHOULD BE APPLIED
                 ARE EXAMPLIFIED HERE:

     EXAMPLE OF CODES FOR CUBIC   : 11 11 11 0 0 0
                          TETRAG  : 11 11 21 0 0 0
            TRIGONAL OR   HEXAGON : 11 11 21 0 0 11   <----------------
                          ORTHOR  : 11 21 31 0 0 0
                          MONOCLI : 11 21 31 0 41 0
                          TRICLIN : 11 21 31 41 51 61
 
                      MONOCLINIC IS FOR beta DIFFERENT FROM 90 DEGREES


       THE RHOMBOHEDRAL CASE IS ALWAYS TO BE TREATED IN TRIGONAL SETTING
  _________________________________________________________________________
  _________________________________________________________________________
  _________________________________________________________________________
  _________________________________________________________________________

  OUTPUT FILES CREATED BY ARITVE:
                 ARCAR.IMP  :  results cycle after cycle
                 ARCAR.PAR  :  intermediate and final new parameters,
                               can be included in ARCAR.DAT
                               in place of the old ones
                 ARCAR1.PRF :  ASCII file containing
                               observed and calculated S(2t)
                               for the first pattern
                               can be seen by DMPLOT
                 ARCAR2.PRF :  ,, for the second pattern

  OPTION OUTPUT
                 ARCAR.OUT  :  Intermediate file giving hkl
                               attribution to each point
                 ARCAR.LT4  :  file containing analogous
                               information as the .PRF files
                 BIDON.DAT  :  Intermediate file 
                 BIDON.IMP  :  Intermediate file
                 BIDON2.IMP :  Intermediate file
                 BIDON.HKL  :  hkl and multiplicity




    ---------------------------------------------------------------
    ---------------------------------------------------------------
                          CPU TIME NEEDED:
  For the test file calculation with ARITVE (90 refinement cycles)
  on a Pentium II 266MHz, the total CPU time was 2 minutes and 14
  seconds.

    ---------------------------------------------------------------
    ---------------------------------------------------------------

 ARCAR.PAR  output file obtained after 1 cycle


 SI1 
  1  0.25522  0.25522  0.25572  0.04000
 SI2 
  1 -0.00776 -0.00776 -0.00776  0.04000
 O1  
  2  0.12533  0.12533  0.12533  0.04000
 O2  
  2  0.66016  0.65969  0.06207  0.12000
      61.67587    351787.0      5000.0    106291.8
      48.46439    593292.5     10000.0    280832.2
       7.15890     7.15890     7.15890    90.00000    90.00000    90.00000

 That file will give the new parameters after each cycle.
 In principle, you have to select the last result and insert it
 in the *.dat file in place of the old parameters.

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 Part of the  ARCAR1.PRF file  obtained after 1 cycle

    This file is suitable for use as data for a graphical output
                          by the DMPLOT program (.prf format)

    Adaptation is easy since the .PRF file contains:
                          2theta-end  2theta-initial Step
                          number of phase , number of points
                          two unused values
                          All observed S(2t)
                          and then all calculated ones:


  91.600   0.000   0.400
  1  230
    1    1
     0.      0.      0.      0.      0.      0.      0.      0.
     0.      0.      0.      0.   2968.   3686.   4804.   6347.
  7884.   8705.   8489.   7535.   6301.   5231.   4480.   3943.
  3539.   3233.   3008.   2867.   2809.   2879.   3443.   4701.
  ......
  5920.   5946.   5978.   6014.   6056.   6101.   6148.   6195.
  6242.   6286.   6325.   6358.   6381.   6394.   6394.   6380.
  6355.   6321.   6279.   6232.   6181.   6128.   6072.   6016.
  5960.   5904.   5849.   5797.   5747.      0.
     0.      0.      0.      0.      0.      0.      0.      0.
     0.      0.      0.      0.   2496.   3717.   5105.   6471.
  7578.   8211.   8257.   7744.   6827.   5732.   4676.   3808.
  3196.   2842.   2712.   2767.   2976.   3313.   3752.   4257.
  .......
  6444.   6438.   6419.   6386.   6343.   6292.   6235.   6174.
  6114.   6056.   6001.   5953.   5910.   5875.   5845.   5821.
  5802.   5785.   5771.   5757.   5742.   5726.   5709.   5690.
  5671.   5651.   5633.   5618.   5608.      0.
 
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   B- Strategy
      This part explains how to proceed. A very important point is
      that your interference functions must be accurate and go to as
      large Q as possible, up to the end of modulations. But the program
      works with S(2t), t for theta (constant wavelength data), see 
      A.C. Wright, J. Non-Cryst. Solids 123 (1990) 129. If you have
      only one data set (i.e. one neutron pattern, or one X-ray),
      then it would be better if your material was a mono-atomic one.
      The ideal case for a di-atomic material is that you have three
      neutron interference functions with isotopic substitutions
      corresponding to large scattering length variations (nevertheless,
      why not adding the X-ray interference function). Of course,
      the more you have data to fit, the more your model will be
      credible. THE "PERFECT" FIT OF ONE INTERFERENCE FUNCTION IN
      THE CASE OF A POLYATOMIC AMORPHOUS MATERIAL IS NOT SUFFICIENT
      FOR CLAIMING THAT YOUR MODEL IS A POSSIBLE ONE ("PERFECT" meaning
      Rp<1% may be).
       
   B-1- The model
     As the Rietveld method, applied to structure refinement from
     powder diffraction data, ARITVE needs a starting structural model.
     The choice of one or several models belongs to the user's
     responsibility. The source of possible models is, as should be
     evident, to be found in some well known structural data base
     (ICSD, Cambridge, Pearson's Handbook of Crystallographic Data for
     Intermetallic phases...). It is also an evidence that
     the models have to be chosen among isoformula crystallized
     compounds with atoms behaving similarly in crystal chemistry.
     However, all amorphous materials have not a formula as simple as
     "SiO2". Thus sometimes several compositions can be chosen in the
     glass forming domain in order to reproduce exactly the formula of
     crystallized compounds known to coexist in the diagram with the
     amorphous ones. That is to say, for structure modelling of amorphous
     materials, THE STRATEGY MAY BEGIN AT THE SYNTHESIS STAGE.
     Suppose that possible crystalline models exist but with different
     kind of atoms (ex: BeF2 instead of SiO2), then you should modify
     the cell parameters of the model in a proportional way to BE
     COHERENT WITH THE ATOMIC DENSITY OF YOUR AMORPHOUS COMPOUND.

   B-2- An order to respect for parameter refinement:
     Once the model has been chosen and all the files prepared, you cannot
     start by refining all parameters. Do not expect that any case will
     work as well as the test case where all parameters are refined
     together and Rp decreases regularly from 8.14 and 5.35 to 3.39 and
     2.90 respectively for neutron and X-ray data after 90 cycles. If
     you try that directly, the calculation may "explode". Remember that
     the test case is a "good" one...
     First you must choose a set of U V W parameter (in order to broaden
     sufficiently the reflection profiles) and perform some cycles
     refining the scale factors only till stabilization of the Reliability
     factor(s) Rp. If there is not any similitude at this stage between
     the observed and calculated interference function, you have not A
     large chance to succeed. You must have Rp<20 or even 10% at this stage.
     Second: adjust U V and W manually or try to refine U and W with
     V fixed to a low value (corresponding to the resolution function
     of the apparatus). The alternate refinement of U, W and then the cell
     parameters can be attempted (or simultaneous, but this is dangerous
     because they are highly correlated).
     Third, the atomic coordinates together with the scale factor
     should be refined. If some atom has a very low scattering
     length for all the interference functions simultaneously,
     then you should not refine its coordinates.
     One must note that the thermal motion effects are considered as
     included in the disorder effect simulated by the line-width
     variation. 

     The above suggestions may not work because the whole process 
     is very unstable... At all stages it is possible
     to compromise the next step by too much a deviation of one
     parameter or another. With the exception of the scale factors,
     the relaxation factors have to limit heavily the variation of
     the refined parameters. Easy fall down to false minima cannot
     be excluded. Remember that each model will have a Rp limit.
     Process slowly in introducing new refined parameters. Do not
     keep new parameters that led to divergency. However, sometimes
     Rp may increase before to decrease.
     

     When significant changes on the cell parameters have been
     observed, the whole first step (preparation of .hkl and .pre
     files) must be done again to be consistent with the new values. 
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   C- What can be expected from ARITVE
     Rietveld application to amorphous materials should be considered
     as one particular approach to their structure modelization:
     essentially a way to test quickly an idea about the possibility
     that there could be some similitude between the mean organization
     in a given amorphous material and the strict tridimensional one
     of a given crystalline structure.
     This method can be used to eliminate wrong models. The method is
     however insufficient to establish the validity or unicity of a
     model, even if the fit is quite "good".
     In all published applications (see the list of references at the 
     beginning of this guide), "good" fit (say Rp < 3%) could be
     obtained with models that showing a few unrealistic
     distances between some atom-pairs. However, the mean distances for
     particular types of pairs were generally credibles. After all,
     this holds also for other methods of simulating amorphous
     material structures, such as molecular dynamics or model-building
     followed by relaxation or Reverse Monte Carlo.

     With this program I tried a lot of models for SiO2 (X-ray + neutron
     data simultaneously fitted) without obtaining a fully 
     satisfying one... The best of the more simple ones is proposed as
     a test of the program, derived from the carnegieite structure.
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   D- How ARITVE could be eventually improved
    For those who are not satisfied by the modest performances
    of ARITVE, some works are suggested:
    The program efficiency would be improved by:

       - Using constraints on distances during refinement, thus
         ensuring the respect of external indications (from EXAFS
         measurements or from well established crystal chemistry). 
       - Generation of the new hkl list at each cycle following
         the eventual cell parameters variation.  

       - Etc...         
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   E- Final recommendations

      - You must not limit yourself to the use of this program, even
        if the results seem satisfying. Try other methods and programs
        as the RMC of McGreevy, molecular dynamics.

      - Any consequence of using this program and consequence of result
        interpretation should not be considered as depending of the
        program author responsibility.

      - This program has not been tested extensively, problems may
        occur...

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      F- BIBLIOGRAPHY - REFERENCES

      References for the original Rietveld method are:
         H.M. RIETVELD   ACTA CRYST. 22,151-152 (1967)
         H.M. RIETVELD   J. APPLIED CRYST. 2, 65-71 (1969)

      ARITVE was built from the multipattern Rietveld program of:
         M.W THOMAS & P.J. BENDALL  ACTA CRYST. A34, 5351 (1978)

      The original text (in French) describing the principle of
      the ARITVE program and some applications may be found in:
         A. LE BAIL, THESE DE DOCTORAT D'ETAT, LE MANS (1985)

      The method together with an application was first introduced
      at the Thirteenth International Congress of Crystallography, 
      9-18 Aout 1984, Hambourg:
         A. LE BAIL & C. JACOBONI, ACTA CRYST. A40, Suppl. C477 (1984)

      Applications and some discussions on the method can be found in:
         A. LE BAIL, C.JACOBONI & R. DE PAPE, J.DE PHYSIQUE, COLL. C8,
            46, 163-168 (1985)
         A. LE BAIL, C. JACOBONI & R. DE PAPE, MATER. SCI. FORUM 6,
            441-448 (1985)
         M. LEBLANC, G. FEREY, J.M. GRENECHE, A. LE BAIL, F. VARRET,
            R. DE PAPE & J. PANNETIER, J.DE PHYSIQUE, COLL. C8, 46,
            175-179 (1985)
         A. LE BAIL, B. BOULARD & C. JACOBONI, MATER. SCI. FORUM,
            19-20, 127-136 (1987)
         M. MARET, P. CHIEUX, J.M. DUBOIS & A. PASTUREL, J. PHYS.:
            CONDENS. MATTER 3, 2801-2817 (1991)

       The glassy SiO2 modelling is in :
   "Modelling the silica glass structure by the Rietveld method,"
   A. Le Bail, J. Non-Cryst. Solids, in press (1995).

       The parallelism with modelling crystallite size/microstrain
       in Rietveld analysis is described in:
         A. LE BAIL, NIST SPECIAL PUBLICATION 846, 142-153 (1992)

       The method has been cited in some review articles:
         A. C. WRIGHT, J. NON-CRYST. SOLIDS 106, 1-16 (1988)
         A. C. WRIGHT, J. NON-CRYST. SOLIDS 123, 129-148 (1990)
         and may be others...
       In these articles, the method was classified in the same
       group as the reverse Monte Carlo method(s), may be improperly.

       In the first version, a strict tan(theta) dependence constraint
       was applied to the FWHM in order to follow exclusively a
       microstrain effect. However, for d(hkl) > dmin, the FWHM was forced
       to be equal to that calculated for dmin (with dmin near of 1.9
       Angstroem). Otherwise the line profiles became Dirac peaks when 
       tan(theta)--> 0. This was a way to take account of the instrumental
       resolution function and eventually a size effect. 
       The present version gives similar results with a Cagliotti-type
       FWHM variation law expected to take account of all possible 
       effects. This law is the classical one used in Rietveld-type
       refinement. A demonstration that this law is able to model
       microstrain and size effect together with the instrumental
       resolution may be found in:
       R.A. YOUNG & P. DESAI, Arkiwum Nauki o Materialach, 10,
                              71-90 (1989). 


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       In case of use, references that may be cited are :
         A. LE BAIL, ARITVE User Guide, Universite du Maine,
                France (2000).
         or
         "Modelling the silica glass structure by the Rietveld method,"
         A. Le Bail, J. Non-Cryst. Solids, in press (1995).


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    G- LIST OF CAUSES OF MAJOR PROBLEMS:
    --------------------------------


    -Your data go at too large angle. It would be better if you limit
     them to nearly 90 2-theta. You could work on your whole dataset
     by a regeneration at a shorter wavelength using interpolation. The
     problem may be that to simulate your data at large angle, the 
     addition of the contributing reflexions occuring up to 180 
     degrees 2-theta are unsufficient.

    -U (and may be V or W) is too large and the last reflections are
     contributing yet to many of the last points of your pattern(s).

    -Non-respect of maximal limits of the program:
            3 patterns
            60000 (hkl) per pattern
            20000 overlapping (hkl) at a diffracting angle
            1200  points per pattern
            70 refined parameters
            4 different atom-type in your sample
            .......

    -Lack of experience in refining crystalline structures. It is not
     recommended to study amorphous without a good knowledge of 
     crystalline compounds and of techniques to determine and refine
     structures from single crystal or powder diffraction data.

    -You have not read this guide...
  

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         GOOD LUCK