title: Ab initio study of ground state MH2, HMHe+ and MHe2(2+), M = Mg, Ca.
abstract: The ground states of MH2, HMHe+ and MHe2(2+) (M = Mg, Ca) have been investigated using relativistically-corrected CCSD(T), IC-MRCI and IC-MRCI+Q, in conjunction with ANO-RCC (Mg, Ca) and aug-cc-pVQZ (H, He) basis sets. The ground states of all magnesium species are predicted to be linear, in agreement with predicted trends. Conversely, HCaHe+ and CaHe2(2+) were determined to be quasi-linear species, with linear-inversion barriers of ca. 115 and 3 cm(-1), respectively. For CaH2, a stationary point on the molecular potential energy surface corresponding to a non-linear equilibrium structure was not observed. Trends in bonding, dissociative potential well-depths and spectroscopic constants for these species have been considered with regards to isoelectronic and isovalent reasoning. These trends are consistent with helium and hydrogen forming electrostatic and covalent bonds with the metal ion, respectively.
authors.affiliation: The Molecular Structure and Detection Group, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Alister J
authors.initials: AJ
authors.lastname: Page
authors.forename: Ellak I
authors.initials: EI
authors.lastname: von Nagy-Felsobuki
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D003198:Computer Simulation; D006371:Helium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007477:Ions; D017616:Magnesium Compounds / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D017610:Calcium Compounds; D007477:Ions; D017616:Magnesium Compounds; D006371:Helium; D006859:Hydrogen