Phonon density of states of silica (SiO2) nanopore via molecular dynamics simulations

TL;DR

This paper uses molecular dynamics and DFT to study the vibrational density of states of silica nanopores, examining effects of temperature, structure, and water adsorption, and compares results with experimental data.

Contribution

It provides a comprehensive computational analysis of silica nanopore VDOS, systematically evaluating force fields and effects of water adsorption, aligning simulations with experimental results.

Findings

VDOS agrees well with DFT and experiments

Temperature has low impact on dry nanopores

Water molecules significantly alter low-energy vibrational modes

Abstract

This study presents a comprehensive computational investigation of the vibration density of states (VDOS) of a silica nanopore, systematically evaluating a range of force fields against inelastic neutron scattering results. We analyze the influence of temperature, crustal structure, and surface-adsorbed water molecules on the nanopore's structural and dynamic properties. We performed classical molecular dynamics simulations of nanopore and bulk silica, and used density functional theory (DFT) calculations for bulk silica for comparison. The resulting VDOS shows relatively good agreement with DFT and experimental data. The temperature has a relatively low effect on the dry nanopore. The inclusion of H2O molecules significantly affects the VDOS. The low-energy modes are dominated by H2O VDOS and increase with loading. This work is an essential step towards characterizing silica nanopores via molecular dynamics and provides a valuable reference for experimental comparison with X-ray and neutron scattering VDOS results.