2008 Volume 9 Pages 8-16
Prediction of crystal structure and property based on computational chemistry is obviously expected as an efficient technology for the developments of new functional material and drug designs. Although the improvement of the prediction accuracy can be resolved by expanding the size of the computational crystal model, the practical performance is often restricted by specification of available computers. In this paper, parallel distributed-computing technique and its performance for a large-scale molecular crystal calculation program CONFLEX/KESSHOU (CONFLEX/K), which is combined our versatile computational chemistry tool CONFLEX and a crystal structure optimization method KESSHOU have been proposed. In order to prevent the calculation accuracy from computational error (loss of trailing digits) on the arithmetic addition between short and long-range interaction energies appearing in the large-scale crystal calculation, the improved Kahan's summation algorithm has been adapted to a part of intermolecular calculations of CONFLEX/K. Finally, we confirmed that CONFLEX/K performance test with crystal structure optimizations of aspirin crystalline having 200-1,000 A crystal radius reaches more than 90% parallel efficiency by using parallel computing environment up to 63 workers (cores). Analysis of crystal energy changes depending on the size of the computational crystal model have shown that if one can expect highly accurate crystal calculation within 10-3 kcal/mol, larger size of the computational crystal model more than 80 A in the crystal radius will be required.
