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Volume 211, 2018
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Identifying pragmatic quasi-harmonic electronic structure approaches for modeling molecular crystal thermal expansion

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Abstract

Quasi-harmonic approaches provide an economical route to modeling the temperature dependence of molecular crystal structures and properties. Several studies have demonstrated good performance of these models, at least for rigid molecules, when using fragment-based approaches with correlated wavefunction techniques. Many others have found success employing dispersion-corrected density functional theory (DFT). Here, a hierarchy of models in which the energies, geometries, and phonons are computed either with correlated methods or DFT are examined to identify which combinations produce useful predictions for properties such as the molar volume, enthalpy, and entropy as a function of temperature. The results demonstrate that refining DFT geometries and phonons with single-point energies based on dispersion-corrected second-order Møller–Plesset perturbation theory can provide clear improvements in the molar volumes and enthalpies compared to those obtained from DFT alone. Predicted entropies, which are governed by vibrational contributions, benefit less clearly from the hybrid schemes. Using these hybrid techniques, the room-temperature thermochemistry of acetaminophen (paracetamol) is predicted to address the discrepancy between two experimental sublimation enthalpy measurements.

Graphical abstract: Identifying pragmatic quasi-harmonic electronic structure approaches for modeling molecular crystal thermal expansion

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Submitted
26 Feb 2018
Accepted
05 Mar 2018
First published
05 Mar 2018

Faraday Discuss., 2018,211, 181-207
Article type
Paper
Author version available

Identifying pragmatic quasi-harmonic electronic structure approaches for modeling molecular crystal thermal expansion

Jessica L. McKinley and G. J. O. Beran, Faraday Discuss., 2018, 211, 181
DOI: 10.1039/C8FD00048D

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