Polarization interactions and boroxol ring formation in boron oxide: A molecular dynamics study

We employ molecular dynamics (MD) simulations to study the structure of vit reous boron oxide. Although six-membered boroxol rings have been observed a t fractions over 60% by various experimental techniques, simulation methods have not produced similar results. We adapt the polarization model, which includes many body polarization effects thought to stabilize such structure s, for boron-oxygen interactions. This model is then used in MD simulations of boron oxide glass at various temperatures. We find a variation in the f raction of rings depending on the temperature of the system during network formation. The maximum ring fraction (similar to 33%) occurs when the sampl e is prepared at low temperatures. At these temperatures, the energy level of boron atoms in rings is 1.6% lower than the energies of boron atoms outs ide of rings. When higher equilibration temperatures are used, the fraction drops to 11%. Thus, two factors are relevant to boroxol ring formation in simulations of boron oxide, a model which incorporates polarization effects or their equivalent, and the appropriate manipulation of temperature histo ry. (C) 2001 American Institute of Physics.