Introduction

NEIGHBOURS is a program for setting up input files in the format that DMAREL 3.02 requires.

The program converts crystallographic data files (CSD FDAT and SHELX) to a cartesian coordinate system. The molecular fragments are treated as rigid identities. It sets up the molecule fixed local axis system on each molecule. The first run of NEIGHBOURS is usually performed to obtain the coordinates of the molecule in the local axis system prior to ab initio calculations. This sets the origin at centre of mass and the local molecular axes parallel to specified intramolecular bonds. The coordinates can be used to calculate the atomic multipoles (DMA) for the electrostatic, or for an ab initio optimisation on the geometry. The program can combine an anisotropic multipoles (DMA), with repulsion-dispersion model. Anisotropic repulsion potentials, requiring definition of local atomic axes at present partly required to be edited in manually.

The program in principle accept all atom types, with 32 default types currently available. It also has this function to allow pasting of a molecular structure (i.e. ab initio derived geometry) into an experimental crystal structure. Two different crystallographic files are accepted as input, they are CSD FDAT file and SHELX file.

Note: DMAREL 3.02 cannot handle linear molecules or very high symmetry space groups occupied by high symmetry molecule.

DMAREL is a lattice energy minimisation program for molecular structures, using a realistic anisotropic atom-atom model for the intermolecular forces. electrostatic model, along with anisotropic repulsion and simple dispersion models. DMAREL needs inverted molecules, and NEIGHBOURS will set them up accordingly. There is a need to convert labels, so that Z' < 1, where there is no inverted and non-inverted atoms in the same molecule. Symmetry information are generated from the FDAT file, using the symmetry information, but also the first letter for the space group is needed to be specified.

A list of publications that are related to or due to the development of the DMAREL program, or applications using DMAREL program is availabled.