Luca

Abstract

The Linear Combination of Atomic Orbitals approach implemented into the public Crystal program for quantum-chemical simulations of n-dimensional periodic systems ( \(n = 0,1,2,3\) ) is here extended to g-type basis functions. A general algorithmic procedure is devised for the calculation of the coefficients needed for the analytical evaluation of one- and two-electron integrals for energy and forces within the recursive McMurchie–Davidson strategy, up to arbitrarily high quantum numbers. Explicit routines are generated for the calculation of all the coefficients needed for g-type functions, which ensure a very high computational efficiency. The code has been generalized in many respects so as to allow for the use of g-type functions for: (1) Hartree–Fock energy and forces; (2) density functional theory energy and forces (in either a local density, generalized gradient, meta-GGA or various hybrid approximations); (3) all-electron and pseudo-potential basis sets; (4) spin-restricted and unrestricted calculations; (5) coupled-perturbed Hartree–Fock/Kohn–Sham (hyper)-polarizability calculations; (6) projected density-of-states. The g-type basis functions are expected to play an important role in (1) the description of the electronic structure of heavy elements and in particular of lanthanides and actinides with occupied 4f and 5f bands, respectively, where they represent the first polarization, (2) those calculations requiring an accurate description of the electronic polarization.

Abstract

Publication date: 1 December 2017
Source:Computational and Theoretical Chemistry, Volume 1121
Author(s): Ali Abbaspour Tamijani
In the recent years, the surfaces of oxides and fluorides have received considerable attention due to their suitability for emerging technologies such as fuel cells. Among these substances, well-known rutile TiO2, and rutile-like SnO2, MgF2 and ZnF2 are of particular interest owing to their utilization in a wide range of applications such as heterogeneous catalysis. In order to probe these materials for their catalytic activity, physisorption of small organic molecules, such as methane, on their respective dominant surfaces is of potential value. However, the lack of adequate experimental results on the adsorption energetics and geometries of binding particles, has stimulated a large number of computational studies. In this work, the van der Waals-driven sorption of CH4 on (110) face of all of the abovementioned structures has been examined computationally. A manifold of dispersion-corrected DFT methods was applied to evaluate the binding and surface energies as well as surface-induced atomic displacements. Only the most energetically favored configuration of the adsorption, has been examined. The calculated values were compared to the pertinent literature data, either theoretical or experimental, when available. Whilst optB86b-vdW produces the most consistent atomic displacements, despite its confinements, revPBE-D3 results in the most accurate adsorption energies for CH4-TiO2(110). Calculated surface energies were in agreement with the prior studies if available.

Graphical abstract