First‐principle modelling of forsterite surface properties: Accuracy of methods and basis sets

Abstract

The seven main crystal surfaces of forsterite (Mg2 SiO4 ) were modeled using various Gaussian-type basis sets, and several formulations for the exchange-correlation functional within the density functional theory (DFT). The recently developed pob-TZVP basis set provides the best results for all properties that are strongly dependent on the accuracy of the wavefunction. Convergence on the structure and on the basis set superposition error-corrected surface energy can be reached also with poorer basis sets. The effect of adopting different DFT functionals was assessed. All functionals give the same stability order for the various surfaces. Surfaces do not exhibit any major structural differences when optimized with different functionals, except for higher energy orientations where major rearrangements occur around the Mg sites at the surface or subsurface. When dispersions are not accounted for, all functionals provide similar surface energies. The inclusion of empirical dispersions raises the energy of all surfaces by a nearly systematic value proportional to the scaling factor s of the dispersion formulation. An estimation for the surface energy is provided through adopting C6 coefficients that are more suitable than the standard ones to describe O-O interactions in minerals. A 2 × 2 supercell of the most stable surface (010) was optimized. No surface reconstruction was observed. The resulting structure and surface energy show no difference with respect to those obtained when using the primitive cell. This result validates the (010) surface model here adopted, that will serve as a reference for future studies on adsorption and reactivity of water and carbon dioxide at this interface.

Interaction of Aromatic Molecules with Forsterite: Accuracy of the Periodic DFT-D4 Method

“…Furthermore, the PBE/DZP method was already tested to reproduce correctly the adsorption properties of small molecules on {010}-fo. 41 To have comparable results, we use the same pseudopotentials for both the PBE and DRSLL functionals. For the case of DRSLL, we set the maximum angular momentum of the Kleinman–Bylander projectors for the H atoms to zero to avoid ghost states for high values of angular momentum.…”

Structure, Stability, and (Non)Reactivity of the Low-Index Surfaces of Crystalline B2O3–I

“…Hybrid functionals have been successfully applied to the investigation of surfaces of a variety of minerals, including diamond, 33 silica, 34, 35 spinel 36 and olivine. 37,38 In CRYSTAL, the multi-electronic wave-function is constructed as an anti-symmetrized product (Slater determinant) of mono-electronic crystalline orbitals (COs) which are linear DFT Exchange and correlation contributions were numerically evaluated by integrating, over the cell volume, functions of the electron density and of its gradient. Choice of the integration grid is based on an atomic partition method, originally developed by Becke.…”

Surface properties of hydrogenated diamond in the presence of adsorbates: A hybrid functional DFT study

“…The computational cost associated with the evaluation of the exact exchange contribution is reduced from N 4 scaling to N 2 -N 3 (where N is the number of atoms making up the system) using GTOs. Thus, allowing the use of hybrid functionals in the study of the geometry and energetics of bare diamond surfaces [19] as well as other surfaces [20][21][22][23].…”

“…In contrast to existing works which use either local or semi-local exchange correlation functionals, hybrid functionals include a portion of Hartree-Fock exchange potential that provides a better representation of the electronic properties. B3LYP has provided exceptional quantitative accuracy in the past, describing the structural and electronic properties of bulk diamond [18], bare diamond surfaces [19], and other insulating material surfaces [20][21][22][23]. This improvement is especially noteworthy with respect to the electronic properties, where local and semi-local functionals fail to provide a correct description.…”