Default parameter file. (c) SAH and Associates 1987. This file is not for commercial use without written permission from SAH. This file contains keywords and parameter values that may be used as defaults by the SHADOW program. If SHADOW does not find this file, or a parameter keyword and associated value (an external default) is not given in this file, SHADOW will assign the suggested value for that parameter indicated below (internal defaults). The keywords below are preceded by an asterisk. If you want to disable an external default, or you want to copy a line for future reference, remove the asterisk from column one. The asterisk must be in column one if there is a keyword following. Recognition of the keywords is case and spacing sensitive: the mix of upper and lower case letters and their spacing must follow those given below. Choose your defaults from the list of choices given for each parameter. If an invalid parameter value is found in the designated position, the suggested value for that parameter will be used. The following mnemonics should be used as a guide to the requested values. The maximum allowed number of digits or characters in the input is indicated by the number of times the mnemonic is repeated. Right justify the value in the indicated field. I - An integer value is required. Do not include a decimal point in the number. R - The numeric value may include a decimal point. A - The value requires one or more characters. You are encouraged to print this file and examine the short description given for each parameter. The full descriptions of these parameters are given in the User's Manual. The suggested parameter values should be adequate for an instrument equipped with a pyrolytic graphite diffracted beam monochromator employing Cu radiation. The following lines are reserved for user notes. ------------------------- Refinement Defaults -------------------------- DEFAULT REFINEMENT PROFILE-SHAPE-FUNCTION Choose the default profile from the following list. The compound profiles explicitly account for the alpha2 (and alpha 3 (sic), if its wavelength and relative intensity are in the instrument calibration file) by using a single-line profile for each of the wavelengths. The position and intensity of the alpha2 (and alpha 3) are fixed with respect to those of the alpha 1. 1 - Gaussian 2 - Lorentzian 3 - Intermediate Lorenztian (IL) 4 - Modified Lorentzian 5 - Pearson VII 6 - Voigt 7 - Pseudo-Voigt 8 - XPS mix, Pseudo-Voigt with fixed coefficient of mixture 9 - Compound PVII: FWHMs and exponents from the calibration curves 10 - Compound PVII: FWHMs and exponents plus delta values 11 - Compound PVII: Unconstrained 12 - Instrument profile convoluted with Lorentzian 13 - Instrument profile convoluted with Gaussian 14 - Instrument profile convoluted with Gaussian*Lorentzian The suggested default is profile 5. This model incorporates a split Pearson VII profile for each wavelength: the shape of the alpha 2 (and alpha 3) line is constrained to take the shape of the alpha 1. Possible values: 1 through 14 Suggested value: 5 Format: .........IIIIIIIIII *Profile 5 SPLIT PROFILE. The state of the flag below determines whether the default profile-shape function is split. This applies to PSF 1-8 only. Possible values: 0 = No, 1 = Yes Suggested value: 1 Format: .........IIIIIIIIII *Split profile 1 COMPOUND PROFILE. The state of the flag below determines whether the default profile-shape function a compound function. This applies to PSF 1-8 only. Possible values: 0 = No, 1 = Yes Suggested value: 1 Format: .........IIIIIIIIII *Compound profile 1 CONSTRAIN ALL PSF SHAPES. The state of the flag below determines whether all profiles in a refinement region are constrained to have the same values for the shape related parameters. This applies to all PSFs. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *PSF shapes same 0 REFINE THE ALPHA2/ALPHA1 RATIO FOR COMPOUND PROFILES. The state of the flag below determines whether the alpha-2/alpha-1 intensity ratio in a compound profile is refined. This flag would most likely have a value of 1 for residual stress analysis since the crystallite population measured for the alpha-1 and alpha-2 lines will most likely not be the same. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Refine a2/a1 0 FWHM MULTIPLIER Value to multiply FWHM values taken from instrument curves for profiles 1-7. The initial values of the FWHM for the non-convoluted profiles are obtained from the profile calibration curves in the file WSGDAT. If the diffraction lines to be refined are extremely wide in comparison to the instrument profiles, the optimization algorithms may not be able to refine the profile parameters. Change the multiplier below to aid in the refinement of very wide profiles, e.g., those from geological or polymer specimens. The FWHM values based on the curves are multiplied by the value below and this result is used as the initial estimate for the FWHM value. Possible value: 0.8 to 25.00 Suggested value: 1.5 Format: .........RRRRRRRRRR *FWHM multiplier 1.5 CONSTRAINTS ON CONVOLUTED PROFILE BROADENING AS A FUNCTION OF ANGLE The integral breadth of profiles 12 and 13 may be constrained to follow relations expected for broadening as a result of small crystallite or strain. If more than one line is being refined then both the size and strain parameters may be refined. It is suggested that the broadening be constrained to follow one or both of the relations. However, as there may be more than one phase or the broadening anisotropic, the defaults do not constrain the broadening. Possible values: 0 = No, 1 = Yes Suggested values: Size 0, Strain 0 Format: .........IIIIIIIIII *Size broad 0 *Strain broad 0 INITIAL ESTIMATES OF CRYSTALLITE SIZE AND STRAIN Initial estimate of crystallite size The value below is used as the initial value for the crystallite size when the convoluted profiles are constrained by size broadening. Possible value: 1 nm to 4000 nm Suggested value: 400.0 <= Provides for a moderately broadened line Format: .........RRRRRRRRRR *Size estimate 160.0 Initial estimate of crystallite strain The value below is used as the initial value for the crystallite strain when the convoluted profiles are constrained by strain broadening. In addition, when the profiles are not constrained by size or strain broadening, the strain value below is used to determine the initial values for the specimen profile FWHM values. Possible value: 1.0E-6 to 1.0 Suggested values: 0.0001856 <= Value taken from SRM640A Si Format: .........RRRRRRRRRR *Strain estimate 0.0001856 PATTERN ASYMMETRY FACTOR An asymmetry function (Rietveld, 1969) can optionally be applied to the profiles within the refinement region. The same asymmetry parameter is refined over all profiles and not on an individual basis. This factor is applied to single-line profiles and to each of the component lines in a compound profile, but it is not used on the convolution profiles. The asymmetry function may be used for all non-convoluted profiles, but there is little benefit in applying it to split-profiles as they are already asymmetric. Since the suggested default for the profile is an asymmetric one, the default for application of the asymmetry parameter will be not to apply it. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Asymmetry 0 LORENTZ/POLARIZATION CORRECTION FOR LINES IN COMPOUND PROFILES Since the position and intensity of the alpha 2 (and alpha 3) lines are fixed with respect to the alpha 1 line in the compound profiles, it is necessary to account for the effects of the Lorentz and polarization factors. You have the option of not applying this adjustment although you are strongly urged to use it. Whether or not the Lorentz factor is applied is determined in the WSGDAT file and can be set using the INSCAL program. If the instrument is a neutron or synchrotron source, you may not need the Lorentz factor. A parameter is necessary to account for the presence, or absence, of a diffracted beam monochromator. This factor is by default set to a value suitable for a graphite diffracted beam monochromator (0.8005). The value of this parameter is found in the WSGDAT file and can be set using the INSCAL program. Apply L/P correction. Possible values: 0 = No, 1 = Yes Suggested value: 1 Format: .........IIIIIIIIII *L/P Correction 1 BACKGROUND ACCOMMODATION DURING THE REFINEMENT PROCESS Background accommodation will depend on whether the background has been previously determined for the pattern, and the state of the flags below. The role of the flags is illustrated in the following flow chart. |--------------------------------| Yes | Use a polynomial background? |--> A polynomial is | "Polynomial bkg" | refined to accommodate |--------------------------------| background | No | Yes |--------------------------------| No |<--| Has background been determined |-->| | | or read from a parameter file? | | | |--------------------------------| | | | | | | | |--------------------------| | | Use calculated background| | | as determined? | | | "Use calc bkg" | | |--------------------------| | | | | | | | | Yes No | | | | | | |----------------------------| | | | Use calculated background | | | | shape, refine offset? | | | | "Use bkg shape" | | | |----------------------------| | | | | | | | | | | | Yes No | | | | ------------>| | | | | ---> The shape of the refined background | | is used but it is allowed "float" | | up and down until the best fit is | | obtained. | | | ---> The previously determined background is used. | | | The background will be assumed <--| equal to zero. No provision will be made to account for it. The suggested technique is to use the background determination algorithm to estimate the background, then use the shape of this curve while refining its offset during profile refinement. If you do not estimate background, then the additive offset should be refined. Refine a polynomial background of order 0-4, 0 being simply an additive offset. -1 means not to use a polynomial. Possible values: -1 = Do not use polynomial, 0-4 = Polynomial order Suggested value: -1 <-Allow the calculated background to be used if it was calculated Format: .........IIIIIIIIII *Polynomial bkg 1 Use calculated background as is. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Use calc bkg 0 Use calculated background shape, refine offset. Possible values: 0 = No, 1 = Yes Suggested value: 1 Format: .........IIIIIIIIII *Ref bkg offset 1 AMORPHOUS PROFILE An amorphous profile can be included in the refinement. This profile will be modeled with a Gaussian function. If you choose to include this profile you will be prompted for the approximate position, intensity and full-width at half-maximum intensity. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Amorphous hump 0 The amorphous profile can be made asymmetric through the use of the Rietveld asymmetry factor. The flag below determines whether the amorphous profile is, by default, asymmetric. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Amorph. asymm. 0 The amorphous profile can be made asymmetric by using a split profile. The flag below determines whether the amorphous profile is, by default, split. Possible values: 0 = No, 1 = Yes Suggested value: 0 Format: .........IIIIIIIIII *Amorph. split 0 OPTIMIZATION ALGORITHM Either a Gauss-Newton or Marquardt optimization algorithm may be used to refine the parameter values. The Gauss-Newton algorithm is the typical least-squares algorithm while the Marquardt is a cross between the traditional Gauss-Newton and a gradient type algorithm: its nature makes it a bit more robust in that it is less sensitive to correlation and poor initial estimates. However, the Marquardt is just a bit slower. The suggested technique is to routinely apply the Gauss-Newton algorithm until a problem with the refinement is encountered, then try the Marquardt algorithm. The third state of this flag will allow you to bypass the refinement of a particular region. This is useful if one region is causing problems and you wish to direct your efforts towards its solution. Possible values: 0 - Bypass, 1 - Marquardt, 2 - Gauss-Newton Suggested value: 2 Format: .........IIIIIIIIII *Opt algorithm 2 REFINEMENT ERROR CRITERION Either the unweighted residual error (R) or the weighted residual error (Rwp) may be used as the refinement criterion. Since the weighted error is statistically correct for X-ray and Neutron data (if the data are collected in the normal step scan mode with fixed collection time at each angle), the weighted error is the suggested default. Possible values: 0 = No, 1 = Yes Suggested value: 1 Format: .........IIIIIIIIII *Rwp error 1 MAXIMUM NUMBER OF REFINEMENT CYCLES Below is the number of refinement cycles to use in the refinement of a set of parameters. Most problems should converge in 5 to 15 cycles. Possible values: 1 to 99 Suggested value: 20 Format: .........IIIIIIIIII *Max. ref. cycles 20 LIMITS FOR PROFILE GENERATION The profiles in SHADOW are generated from the peak position outwards. The following parameter tells SHADOW when to stop. If the parameter value is positive, the profiles are generated until they reach a minimum limit in COUNTS. If the parameter value is negative, the profiles are generated to a fractional value of the peak intensity given by the (absolute value of the parameter) x (the peak intensity). Possible value: +value - absolute count limit -value - fractional limit Suggested values: 0.1000 <= Generate all profiles to 0.1000 COUNTS Format: .........RRRRRRRRRR *Limit of PSF 0.1000 PLOTTING OF THE REFINEMENT RESULTS The results after refinement can optionally be plotted. The default file name for the refinement plots is called RPLOT. You may want to use a SET command to direct the output to another file name. (Refer to the DOS manual for information regarding the SET command). Possible values: 0 - No, 1 - Yes Suggested value: 1 Format: .........IIIIIIIIII *Refinement plots 1 --------------------- Line List Function Defaults ---------------------- STATISTICAL WEIGHTING DURING LINE LIST REGRESSION ANALYSES The recorded set of refined line parameters can be used to determine parameters, e.g., crystallite size and strain, based on the results of regression analyses. Since the error varies with each refined parameter, each parameter should be weighted by 1/variance. The following flag indicates whether the recorded standard deviations for the line parameters should be used as statistical weighting during any analyses performed under the "Line List Functions" options menu. Possible values: 0 - No, 1 - Yes Suggested value: 1 Format: .........IIIIIIIIII *Wgt. line params 1 --------------------------- Search Defaults ---------------------------- MINIMUM STANDARD DEVIATION ABOVE BACKGROUND FOR PEAK ACCEPTANCE One of the considerations in determining whether a point is a possible peak is based on the number of standard deviations the point is above background. This standard deviation of a point in the pattern is calculated as follows: STD = square root( bkg-intensity + point-intensity ) where bkg-intensity is the background as determined by the background evaluation routine, and the point-intensity is the collected intensity at the point. Note that the value of this parameter is only effective when the background has been determined. Possible values: Any non-negative value Suggested value: 3.0 Format: .........RRRRRRRRRR *STD above bkg 3.0 MINIMUM RELATIVE INTENSITY A point will not be considered as a peak if its intensity relative to the intensity of the largest peak found is below a user defined minimum. If background has been determined, the minimum on relative intensity may be redundant with the number-of-standard-deviations parameter above. However, if background has not been determined, this parameter will control the number of extraneous points printed in the peak search list whereas the former will not. The default of 1% may be too high in those cases where the relative intensities of the lines vary considerably. However, if the background has not been determined, this value may serve adequately. The user must examine the search results to determine if low intensity lines are being excluded from the peak search results. Possible values: Any non-negative value Suggested value: 1.0 Format: .........RRRRRRRRRR *Min peak rel int 1.0 NUMBER OF POINTS USED IN THE PEAK SEARCH A second order polynomial peak finding algorithm is used to locate peaks in the data. The user may specify the number of points in the polynomial curve to use. The higher the number of points, the less susceptibility to finding spurious points. However, as the number of points increases, the sensitivity of the peak finder decreases and hence, very sharp, well defined lines may be missed. The suggested value of 7 leans towards the sensitive side and hence may produce a listing with spurious peaks in patterns with diffuse maxima. The user should adjust this value until acceptable results are obtained. Possible values: An odd integer between 5 and 25 inclusive. Suggested value: 7 Format: .........IIIIIIIIII *Pts peak finding 7 NUMBER OF POINTS TO USE IN DATA SMOOTHING The degree of smoothing is determined by the number of points used by the smoothing algorithms. As the number of points increases, the data are smoothed to a greater degree with a corresponding loss in resolution. The suggested value of 7 leans towards a light smoothing and will not fold two neighboring peaks together. The user should adjust this value until acceptable results are obtained. Possible values: An odd integer between 5 and 25 inclusive. Suggested value: 7 Format: .........IIIIIIIIII *Pts smoothing 7 TYPE OF FILTER FOR DATA SMOOTHING You have three choices in the type of smoothing to apply to your data: 0 - Bromba/Ziegler filter: a recursive filter using integers 1 - Savitsky/Golay filter: a non-recursive filter, the most widely used digital filtering algorithm, and 2 - No filter. The suggested default Bromba/Ziegler filter has some unique properties including using integer arithmetic (fast) and does not propagate errors as it proceeds through the data. However, you may notice integer overflows if the number of points in the filter is large and the intensities of your data are also large. The theory of this filter and the Savitsky/Golay are identical so if problems with high degrees of smoothing are encountered, you should switch to the Savitsky/Golay filter. Possible values: 0 - Bromba/Ziegler, 1 - Savitsky/Golay, 2 - No filter Suggested value: 0 Format: .........IIIIIIIIII *Filter type 0 DIGITAL FILTER MOMENT The filters may be thought of as polynomial curves; the filter moment specifies the degree of the polynomial to use. 0 - An "averaging" filter 2 - A quadratic filter 4 - A quartic filter As the filter moment increases, the filter will distort sharp peaks to a lesser degree. However, a filter with a high moment may not smooth satisfactorily. A moment of 2 is adequate in most cases. If the data contain *only* sharp peaks, a moment of 4 may be advantageous. Possible values: Bromba/Ziegler = 0,2,4 Savitsky/Golay = 2 Suggested value: 2 Format: .........IIIIIIIIII *Filter moment 2 PLOTTING OF THE SEARCH RESULTS The search results can optionally be plotted. The default file name for the refinement plots is called SPLOT. You may want to use a SET command to direct the output to another file name. (Refer to the DOS manual for more information regarding the SET command). Possible values: 0 - No, 1 - Yes Suggested value: 1 Format: .........IIIIIIIIII *Search plots 1 -------------------- Background Evaluation Defaults -------------------- BACKGROUND HANDLING The value of this flag determines the default method of handling the background in a pattern when the pattern is opened or the background determination option is chosen from the main menu. Possible values: 0-4 - Polynomial, -1 - Skip. -2 - INSCAL background. Suggested value: 1 <-- Relatively safe and generic. Base value on problem. Format: .........IIIIIIIIII *BKG handling 1 BACKGROUND PLOT This flag determines whether a plot file containing background data is generated by default. Possible values: 0 - No, 1 - Yes Suggested value: 0 Format: .........IIIIIIIIII *BKG plots 0 -------------------------- Plot File Defaults -------------------------- PLOT FILE FORMAT Plot files can either be written with formatted for unformatted records. Unformatted plot files can be processed faster by programs and may be about 50%-60% of the size of formatted files. However, unformatted files cannot be transferred from one type of computer to another, e.g., PC to mainframe. The plot file type indicated below should match the default plot file type in XRDPLT.DFT easiest use although XRDPLT can be told the plot file type at the time the file name is given. Also note that the CONPLT program can be used to convert between formatted and unformatted plot files. Possible values: 0 - Unformatted, 1 - Formatted Suggested value: 0 Format: .........IIIIIIIIII *Format plot file 0