[gdiscuss] Support for 2D XTL files?

[Keith Refson <Keith.Refson@earth.ox.ac.uk>]

How easy would it be to support the 2-D Insight XTL files generated by
Cerius2?  These have the following format:

TITLE caco3-5116 from Cerius2
DIMENSION 2
CELL
  12.51664   15.34671   78.82407
SYMMETRY  LABEL P1
SYM MAT  1.0  0.0  0.0  0.0  1.0  0.0  0.0  0.0  1.0 0.0000 0.0000 0.0000
 
ATOMS
NAME       X          Y          Z     CHARGE   TEMP    OCCUP   SCAT
  CA    0.01428   -0.02268   -0.19534  2.0000  0.0000  1.0000   CA2+
  CA    0.51820   -0.01772   -0.32523  2.0000  0.0000  1.0000   CA2+
  CA    0.34431    0.79267   -0.95245  2.0000  0.0000  1.0000   CA2+
  CA    0.84723    0.79213   -0.98844  2.0000  0.0000  1.0000   CA2+
  CA    0.18437    0.59435   -1.56634  2.0000  0.0000  1.0000   CA2+

The main differences seem to be the DIMENSION 2 keyword and the
specification of A, B and GAMMA only.  One awkward feature is that the
X and Y co-ordinates are fractional and the Z is cartesian and unscaled.

I had a quick play with the code in file.c and got it to do *most* of
what is needed, ie read in the co-ordinates and unit cell.  However to
cope with the fact that the z co-ords are cartesian I simply defined
data->pbc[2] = 1.0.  This is not consistent with the way MARVIN files
data->are handled. Is this an easy or difficult thing to fix?

Ideally I'd like to be able to read in a 2X XTL file from Cerius, edit
it and possibly write it as a MARVIN restart file, if there was some
way to define regions.

Here are my hacked up changes for inspection.

xtl2d

Keith Refson
-- 
Dr Keith Refson,        "Paradigm is a word too often used by those who would
Dept of Earth Sciences      like to have a new idea but cannot think of one." 
Parks Road,                  -- Mervyn King, Deputy Governor, Bank of England
Oxford OX1 3PR, UK        
Keith.Refson@                       Tel: 01865 272026
             earth.ox.ac.uk         Fax: 01865 272072