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Issue 44, 2019
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Revised values for the X23 benchmark set of molecular crystals

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We present revised reference values for cell volumes and lattice energies for the widely used X23 benchmark set of molecular crystals by including the effect of thermal expansion. For this purpose, thermally-expanded structures were calculated via the quasi-harmonic approximation utilizing three dispersion-inclusive density-functional approximations. Experimental unit-cell volumes were back-corrected for thermal and zero-point energy effects, allowing now a direct comparison with lattice relaxations based on electronic energies. For the derivation of reference lattice energies, we utilized harmonic vibrational contributions averaged over four density-functional approximations. In addition, the new reference values also take the change in electronic and vibrational energy due to thermal expansion into account. This is accomplished by either utilizing experimentally determined cell volumes and heat capacities, or by relying on the quasi-harmonic approximation. The new X23b reference values obtained this way will enable a more accurate benchmark for the performance of computational methods for molecular crystals.

Graphical abstract: Revised values for the X23 benchmark set of molecular crystals

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The article was received on 13 Aug 2019, accepted on 12 Oct 2019 and first published on 15 Oct 2019

Article type: Paper
DOI: 10.1039/C9CP04488D
Phys. Chem. Chem. Phys., 2019,21, 24333-24344

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    Revised values for the X23 benchmark set of molecular crystals

    G. A. Dolgonos, J. Hoja and A. D. Boese, Phys. Chem. Chem. Phys., 2019, 21, 24333
    DOI: 10.1039/C9CP04488D

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