Compilation of Ionic Clusters with the Rock Salt Structure: Accurate Benchmark Thermochemical Data, Assessment of Quantum Chemistry Methods, and the Convergence Behavior of Lattice Energies

Abstract

In the present study, computational quantum chemistry is used to obtain lattice energies (LEs) for a range of ionic clusters with the NaCl structure. Specifically, the compounds include NaF, NaCl, MgO, MgS, KF, CaO, and CaS clusters, (MX) n , with n = 1, 2, 4, 6, 8, 12, 16, 24, 32, 40, 50, 60, 75, 90, and 108. The highest-level W2 and W1X-2 methods are applied to the small clusters with n = 1 to 8 (the MX35 data set). The assessment with MX35 shows that, for the calculation of geometries and vibrational frequencies, the PBE0-D3­(BJ) and PBE-D3­(BJ) DFT methods are reasonable, but the calculation of atomization energies is more challenging. This is a result of different systematic deviations for clusters of different species. Thus, species-specific adjustments are applied for larger clusters, which are calculated with the DuT-D3 double-hybrid DFT method, the MN15 DFT method, and the PM7 semi-empirical method. They yield smoothly converging LEs to the bulk values. It is also found that, for the alkali-metal species, the LEs for a single molecule are ∼70% of the bulk values, while for the alkali-earth species, they are ∼80%. This has enabled a straightforward means to the first-principles estimation of LEs for similarly structured ionic compounds.

Sorting drug conformers in enzyme active sites: the XTB way

“…53 As a sanity check, we have briefly examined the two methods with several collection of thermochemical properties that we have previously used (ESI †). 63,64 In general, we indeed find XTB2 yielding smaller deviations than those for XTB1. We reiterate that, for the MEI196 data set, the MAD of 18.2 kJ mol À1 for the absolution binding energies for XTB2 is just slightly larger than that for XTB1 (16.6 kJ mol À1 ).…”

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

“…In contrast, while B3LYP-D3BJ is the best-performing method for the DAPD set, its deviation for Pd 2 is substantial (−66.9 kJ mol –1 ). To investigate larger Pd clusters with B97-D3BJ, which may be the most suitable method for systems related to Pd 2 , would complement our previous studies into the convergence behavior from molecular to material systems for other species such as fullerenes, − graphene, , gold clusters, and ionic compounds. , However, it is unclear how well will B97-D3BJ perform for larger systems based on just one data point on the smallest system.…”

“…The stringent requirements for transition metals have contributed to fewer high-quality computational data being obtained in comparison with main-group species, for which well-known large data sets are available. , Nonetheless, efforts have continued to be made in closing this gap (see, for example, refs − ). In recent years, we have produced several thermochemistry data sets of transition-metal species, with values of the quality of ∼CCSDT­(Q) at the complete-basis-set (CBS) limit. , They complement our earlier studies into a different set of transition-metal reactions, as well as investigations of other systems that are challenging to computational chemistry. − …”