Subject: crystal packing calculations and programs

From: [email-masked] (Douglas A. Smith Ph.D.)
Date: Sat, 1 Feb 1997 09:52:51 -0500

A very interesting (to me) paper has just appeared in J. Phys. Chem. B,
1997, 101, 798 by Sorescu, Rice and Thompson.  In this paper, they dev3elop
an intermolecular potential for RDX
(hexahydro-1,3,5-trinitro-1,3,5-s-triazine) and perform crystal packing, MC,
and MD studies.

The authors parameterize their  potential based on the known neutron
diffraction structure of RDX.  They also reference several other packages
for performing crystal packing calculations.

What are the options when one does not have the crystal structure available?
Can one reasonably start from a high quality ab initio calculation on a
single molecule (gas phase) and use that structure to pack a crystal?  If
one does, what is the likelihood of getting the crystal structure correct?
Or does one need to perform ab initio calculations in the periodic solid
(e.g., CRYSTAL 95 calculations) before performing crystal packing?

What packages are out there, commercial and "public domain" (free, QCPE,
etc.) that can perform crystal packing calculations?  I would like to
predict space group, density, lattice energy, etc.

Perhaps, since there are pedagogical questions here rather than just a
request for pointers to software, we could keep this discussion public on
the CCL, not just a series of replies directly to me.

Doug
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