Molecular-dynamics study of the structural correlation of porous silica with use of a parallel computer

Molecular-dynamics simulations of porous silica, in the density range 2.2--0.1 g/cm³, are carried out on a 41 472-particle system using a multiple-instruction multiple-data parallel computer. An effective interatomic potential consisting of two-body and three-body covalent interactions is used. Structural correlation is analyzed using the pair-distribution function, neutron-scattering structure factor, and bond-angle distribution. The internal surface area, pore surface-to-volume ratio, pore-size distribution, fractal dimension, correlation length, and mean-particle size are determined as a function of the density. Structural transition from the condensed amorphous phase to the low-density porous phase is characterized by these quantities. Various dissimilar porous structures are prepared by controlling the preparation condition.