Thermal Expansion in Dispersion-Bound Molecular Crystals
Abstract
We explore how anharmonicity, nuclear quantum effects (NQE), many-body dispersion interactions, and Pauli repulsion influence thermal properties of dispersion-bound molecular crystals. Accounting for anharmonicity with molecular dynamics yields cell parameters accurate to within 2% of experiment for a set of pyridine-like molecular crystals at finite temperatures and pressures. From the experimental thermal expansion curve, we find that pyridine-I has a Debye temperature just above its melting point, indicating sizable NQE across the entire crystalline range of stability. We find that NQE lead to a substantial volume increase in pyridine-I (% more than classical thermal expansion at K) and attribute this to intermolecular Pauli repulsion promoted by intramolecular quantum fluctuations. When predicting delicate properties such as the thermal expansivity, we show that many-body dispersion interactions and sophisticated treatments of Pauli repulsion are needed in dispersion-bound molecular crystals.
Cite
@article{arxiv.1803.00536,
title = {Thermal Expansion in Dispersion-Bound Molecular Crystals},
author = {Hsin-Yu Ko and Robert A. DiStasio and Biswajit Santra and Roberto Car},
journal= {arXiv preprint arXiv:1803.00536},
year = {2018}
}