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SUBROUTINE XROOT(IA,XX,IS,IL,C)

Finds the symmetry operations which take the given source atom
into the given coordinates.

Arguments:

On entry IA is the number of the atom in the given list on A cards
XX is a 1x3 real array holding the given x,y,z to be identified.

On exit IS the number of the necessary symmetry operator, set -ve if
the (-x, -y, -z) operator is also required; if no such operator is found, IS=0

IL is the number of the necessary lattice translation.
C is a 1x3 real array holding any necessary cell translations,
which will be whole numbers.

Prerequisite calls:

The symmetry should have been read by SYMOP, and the atomic positions by ATOPOS.

Notes:

There is an inverse subroutine XTRANS
Does not now involve the putting of a transformed atom back into a central cell, because this had awkward repercussions in slack constraints.

Calls:

GMADD GMREV GMSAME ROTSYM

Called by:

RDATOM

Common blocks used:

/NSYM/ to use NCENT NOPC NLAT
/SYMDA/ to use TRANS ALAT

*** XROOT updated by JCM 18 Oct 87 ***

Classification:

Crystal Geometry . . . . . . . Crystallographic

SUBROUTINE XTRANS(IAT,XX,IS,IL,C)

Transforms a given atomic position by given symmetry operator and
lattice and cell translations.

Arguments:

On entry IAT = which atom
IS = which symmetry operator, -ve if -x,-y,-z
IL = which lattice translation
C is a 1x3 real array holding cell translations in the x, y and
z directions, which will usually be integers.

On exit XX is a 1x3 real array holding the transformed coordinates

Prerequisite calls:

The symmetry should have been set up by SYMOP, and the atomic positions by ATOPOS.

Notes:

There is an inverse subroutine XROOT
Altered not to put atom into central cell after symmetry transformations because this has awkward repercussions in slack constraints

Calls:

GMADD GMREV ROTSYM

Called by:

ATOMS GEOMCO RDATOM

Common blocks used:

/SYMDA/ to use TRANS ALAT

*** XTRANS corrected by JCM 18 Oct 87 ***

Classification:

Crystal Geometry . . . . . . . Crystallographic

SUBROUTINE XYZREL

Collects all position parameter constraints implied by the
symmetry.

Description:

Space group symmetry generated constraints are each between 2 parameters.
Some of the relations found may lead to fixings rather than constraints.
On exit in /POSREL/ for each atom I the integer array NXYZ(I,1:3) and real array XYZ(I,1:3) hold the constraints.

Calls:

GMEQ GMREV JGMZER RELSM3

Common blocks used:

/POSNS/ to use NATOM ISGEN
/POSREL/ to use all members
/SYMDA/ to use SYM

*** XYZREL by JCM 28 Nov 91 ***

Classification:

General Least Squares Refinement . . . . . . . Crystallographic

Contents Manual
P. Jane Brown e-mail: brown@ill.fr
Institut Laue Langevin,
Grenoble, FRANCE