Molecular dynamics (MD) simulation using force fields is widely used to investigate structure and properties of materials at atomistic level. However, since atomic motions are controlled by classical mechanics, some thermodynamic properties that are governed by quantum effects are unrealistic (cf. the calculated molar heat capacity is always close to 3R, where R is the gas constant). Thermal vibration is essentially a quantum mechanical phenomenon, and the high frequency vibrations such as O-H stretching cannot be excited at room temperature. In this study we showed that realistic vibrations at given temperatures can be estimated by frequency filtration from the Bose-Einstein distribution. Based on this new approach, the molecular origin of the thermal expansion behaviour of the crystals of cellulose and chitin was reinterpreted.

Frequency filtration to obtain realistic thermal vibrations in crystal from molecular dynamics

249th National Meeting (2015)

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