Spectroscopic Properties of MgH₂, MgD₂, and MgHD Calculated from a New ab Initio Potential Energy Surface

Abstract

A three-dimensional potential energy surface for the ground electronic state of MgH 2 has been constructed from 9030 symmetry-unique ab initio points calculated using the icMRCI+Q method with aug-cc-pVnZ basis sets for n ) 3, 4, and 5, with core-electron correlation calculated at the MR-ACPF level of theory using cc-pCVnZ basis sets, with both calculations being extrapolated to the complete basis set limit. Calculated spectroscopic constants of MgH 2 and MgD 2 are in excellent agreement with recent experimental results: for four bands of MgH 2 and one band of MgD 2 the root-mean-square (rms) band origin discrepancies were only 0.44 and 0.06 cm -1 , respectively, and the rms relative discrepancies in the inertial rotational constants (B [V] ) were only 0.0196% and 0.0058%, respectively. Spectroscopic constants for MgHD were predicted using the same potential surface.

Organomagnesium clusters: Structure, stability, and bonding in archetypal models

“…It is well-known that magnesium dihalides are linear although this is not the case for all alkaline earth dihalides [12,30,37]. Our BP86/TZ2P distances are quite close to the experimental ones for MgH 2 (1.69582(4) obtained with microwave spectroscopy [38,39]), MgCl 2 (2.162 AE 0.005 Å [40] and 2.1856 AE 0.0114 Å [41] both obtained by electron diffraction). Unfortunately, for Mg(CH 3 ) 2 only the data for the MgeC distance in the polymeric solid is available (2.…”

Mg2H2: New insight on the Mg–Mg bonding and spectroscopic study

“…40 Finally the hydrogen exchange energies, Mg + H 2 → MgH + H, agree similarly. These reactions can be involved in hydrogen storage phenomena.…”

“…27,28 Among the species involved in reaction 1, the simplest gaseous MgH, a prototype of other magnesium hydride compounds, also presents a large importance for astrophysicists, concerning the studies of stellar atmospheres and for estimating the relative metal abundance in some galaxies. Accurate calculations on this molecule were recently performed by Li and Le Roy 40 and Hrenar et al 41 Experimental detection and characterization of this species was made in rare gas matrices 10,11,14 and in gas phase by Shayestch et al, 42 where MgH 2 was formed by the electrical discharge in a high temperature furnace, allowing the measurement of its rovibrationally resolved emission spectrum. 38,39 Concerning the triatomic species, MgH 2 has been proven to be an intermediate in reaction 1.…”

Pathways and reduced-dimension five-dimensional potential energy surface for the reactions H3++CO→H2+HCO+ and H3++CO→H2+HOC+

“…33 Finally, the all-electron correlation at the complete basis limit CBS͑V+C͒ was obtained as a sum of the energies of CBS͑V͒ and CBS͑C͒ using the detailed strategy described in Ref. 35. To check for the effect of coupling from excited electronic states, the six lowest states along the MEP for the collinear reaction H 3 + +CO→ H 2 + HCO + were explored by performing state-averaged complete active space self-consistent-field ͑CASSCF͒ calculations with equal weights using the aug-cc-pVTZ basis sets.…”