Classical and path integral molecular dynamics (PIMD) simulations are used tostudy alpha-quartz and beta-quartz in a large range of temperatures at zeroexternal stress. PIMD account for quantum fluctuations of atomic vibrations,which can modify material properties at temperatures below the Debyetemperature. The difference between classical and quantum mechanical resultsfor bond lengths, bond angles, elastic modulii, and some dynamical propertiesis calculated and comparison to experimental data is done. Only quantummechanical simulations are able to reflect the correct thermomechanicalproperties below room temperature. It is discussed in how far classical andPIMD simulations can be helpful in constructing improved potential energysurfaces for silica.
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