A method of calculating molecular crystal structures

A novel method of calculating the molecular position in a lattice of known dimensions is presented. The repulsive lattice energy is approximated by a sum of quadratic nonbonded interatomic potential functions and the lattice energy sum is minimized by full-matrix least squares. The convergence range from arbitrary trial models is greater than the previously used steepest descent method using (exp-6) nonbonded potentials. Greatly increased speed of convergence is also obtained because of the inclusion of off-diagonal terms and the small number of repulsive interactions which are considered. The calculated packing models are sufficiently accurate to serve as a starting point for structure factor least-squares refinement based on diffraction data.