High precision quantum-chemical treatment of adsorption: Benchmarking physisorption of molecular hydrogen on graphane

Abstract

A multilevel hierarchical ab initio protocol for calculating adsorption on non-conducting surfaces is presented. It employs fully periodic treatment, which reaches local Møller-Plesset perturbation theory of second order (MP2) with correction for the basis set incompleteness via the local F12 technique. Post-MP2 corrections are calculated using finite clusters. That includes the coupled cluster treatment in the local and canonical frameworks (up to perturbative quadruples) and correlated core (with MP2). Using this protocol, the potential surface of hydrogen molecules adsorbed on graphane was computed. According to the calculations, hydrogen molecules are adsorbed on graphane in a perpendicular to the surface orientation with the minimum of the potential surface of around -3.6 kJ/mol located at the distance of 3.85 Å between the bond center of the hydrogen molecule and the mid-plane of graphane. The adsorption sites along the path from the downward-pointing carbon to the ring center of the graphane are energetically virtually equally preferable, which can enable nearly free translations of hydrogen molecules along these paths. Consequently, the hydrogen molecules on graphane most likely form a non-commensurate monolayer. The analysis of the remaining errors reveals a very high accuracy of the computed potential surface with an error bar of a few tenths of a kJ/mol. The obtained results are a high-precision benchmark for further theoretical and experimental studies of hydrogen molecules interacting with graphane.

Periodic and fragment models based on the local correlation approach

“…correction actually consists of several components evaluated with different clusters. It is possible to obtain, in the periodic regime, the LMP2 result close to the basis set limit (using LMP2-F12; Usvyat, 2013) as well as the core correlation at the LMP2 level (Martinez-Casado et al, 2014). The basis set correction, however, is of relatively shortrange, provided that the periodic LMP2 basis set is sufficiently good, say, of augmented-triple-zeta quality.…”

“…First, the algorithms have to be adapted for translating the intermediates on the fly to make their contractions efficient. This often requires that batches of intermediate quantities, that have to be kept in memory simultaneously, should contain the complete cell-index ranges (Maschio et al, 2007;Usvyat, 2013).…”

“…The first real periodic correlation method, applicable to 3D as well as to 2D, 1D, and 0D periodic crystals, was the local MP2 (LMP2) method implemented in the Cryscor program (Maschio, 2011;Maschio et al, 2007;Pisani et al, 2005Pisani et al, , 2008Pisani et al, , 2012Schütz et al, 2010;Usvyat, 2013;Usvyat et al, 2015;. The Hartree-Fock reference orbitals are provided by the Crystal program ) that uses a basis set of atom-centered Gaussiantype orbitals (GTOs).…”

“…Another popular choice of the lower-order periodic treatment is DFT (Boese & Sauer, 2013;Rubes & Bludsky, 2008;Taylor et al, 2012;Tosoni & Sauer, 2010;Tuma & Sauer, 2006). Recently, with the development of periodic correlated techniques, the periodic local MP2 was used as the lower-level method (Martinez-Casado et al, 2014;Müller & Usvyat, 2013;Tsatsoulis et al, 2017;Usvyat, 2015).…”

Strong 1D localization and highly anisotropic electron–hole masses in heavy-halogen functionalized graphenes

“…32,33 For C, F and H, basis sets were constructed according to the procedure described by Usvyat. 34 In all cases the description of the vacuum region was enhanced by adding ghost atoms containing a 1 s function with an exponent of 0.06 a 0…”