Ab-initio simulation of Hench bioglass

Abstract

The B3LYP ab-initio periodic simulation of the Hench 45S5® Bioglass (45% SiO2 – 24.5% Na2O – 24.5% CaO – 6% P2O5) using large unit cells (between 300 and 500 atoms) will be performed using the massive parallel version of CRYSTAL06 which solves the Schroedinger equation adopting Gaussian type basis functions. The code can exploit the availability of a large number of CPUs and shared memory by subdividing the most demanding tasks (two-electron integrals, matrix diagonalization, energy gradient, DFT grid generation, etc.) so that ab-initio calculations with more than 15000 atomic orbitals are within reach. Structures, electronic features (Mulliken net charges, band structure, nuclear electric field gradient) and harmonic vibrational frequencies computed at gamma point of complex bioglasses will be the by-products of the ab-initio simulation. These data will allow predicting and interpreting, at the atomic level, the experimental infrared and Raman spectra of a bioglass. Vibrational analysis will also provide the cation (Na and Ca) mobility which is crucial to understand the Hench mechanism. The starting structures (at variable phosphorous content) for the ab-initio simulation are provided by molecular dynamics calculations based on literature general force fields. The refinement of the force field to become more specific and accurate for the bioglasses modelling will also be an important by-product of the ab-initio results.