Modified Density Functional Dispersion Correction for Inorganic Layered MFX Compounds (M = Ca, Sr, Ba, Pb and X = Cl, Br, I)
| Autor: | Elfi Kraka, Daniel Sethio, Latévi Max Lawson Daku, Hans Hagemann, João B. L. Martins |
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| Rok vydání: | 2020 |
| Předmět: |
Phase transition
010304 chemical physics Chemistry Analytical chemistry Noble gas Crystal structure 010402 general chemistry 01 natural sciences 0104 chemical sciences Ion Tetragonal crystal system symbols.namesake Lattice constant ddc:540 0103 physical sciences symbols Van der Waals radius Physical and Theoretical Chemistry Dispersion (chemistry) |
| Zdroj: | Journal of Physical Chemistry. A, Vol. 124, No 8 (2020) pp. 1619-1633 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.9b10357 |
| Popis: | MFX (M = Ca, Ba, Sr, Pb and X = Cl, Br, I) compounds have received considerable attention due to their technological application as X-ray detectors, pressure sensors, and optical data storage materials, when doped with rare-earth ions. MFX compounds belong to the class of layered materials with a tetragonal Matlockite crystal structure, characterized by weakly stacked double-halide layers along the crystallographic c-axis. These layers predominantly determine phase transitions, elastic, and mechanical properties. However, the correct description of the lattice parameter c is a challenge for most standard DFT functionals, which tend to overestimate the lattice parameter c. Because of the weak interactions between the halide layers, dispersion-corrected functionals seem to be a better choice. We investigated 11 different inorganic layered MFX compounds for which experimental data are available, with standard and dispersion-corrected functionals to assess their performance in reproducing the lattice parameter c, structural, and vibrational properties of the MFX compounds. Our results revealed that these functionals do not describe the weak interactions between the halide layers in a balanced way. Therefore, we modified Grimme's popular DFT-D2 dispersion correction scheme in two different ways by (i) replacing the dispersion coefficients and van der Waals radii with those of noble gas atoms or (ii) increasing the van der Waals radii of the MFX atoms up to 40%. Comparison with the available experimental data revealed that the latter approach applied to the PBE (Perdew–Burke–Ernzerhof)-D2 functional with 30% increased van der Waals radii, which we coined PBE-D2* (Srvdw 1.30) is best suited to fine-tune the description of the weak interlayer interactions in MFX compounds, thus significantly improving the description of their structural, vibrational, and mechanical properties. Work is in progress applying this new, computationally inexpensive scheme to other inorganic layered compounds and periodic systems with weakly stacked layers. |
| Databáze: | OpenAIRE |
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