Structures and Heats of Formation of Simple Alkali Metal Compounds: Hydrides, Chlorides, Fluorides, Hydroxides, and Oxides for Li, Na, and K

Abstract

Geometry parameters, frequencies, heats of formation, and bond dissociation energies are predicted for simple alkali metal compounds (hydrides, chlorides, fluorides, hydroxides and oxides) of Li, Na, and K from coupled cluster theory [CCSD(T)] calculations including core-valence correlation with the aug-cc-pwCVnZ basis set (n = D, T, Q, and 5). To accurately calculate the heats of formation, the following additional correction were included: scalar relativistic effects, atomic spin-orbit effects, and vibrational zero-point energies. For calibration purposes, the properties of some of the lithium compounds were predicted with iterative triple and quadruple excitations via CCSDT and CCSDTQ. The calculated geometry parameters, frequencies, heats of formation, and bond dissociation energies were compared with all available experimental measurements and are in excellent agreement with high-quality experimental data. High-level calculations are required to correctly predict that K(2)O is linear and that the ground state of KO is (2)Sigma(+), not (2)Pi, as in LiO and NaO. This reliable and consistent set of calculated thermodynamic data is appropriate for use in combustion and atmospheric simulations.

Ab initiopotentials ofF+Li2accessible at ultracold temperatures

“…We have conducted ab initio (MRCI + Q) calculations using a VQZ basis on lithium and an AVQZ basis on fluorine for the lowest two states of the LiF molecule and determined a D e value of 47 991 cm −1 (574.1 kJ mol −1 ), which lies within the uncertainty range of the experimental value 577 ± 21 kJ mol −1 . This value is also in good agreement with a recent CCSD(T) study [34] obtained at the complete basis set limit (and including relativistic and spin-orbit corrections) by Vasiliu et al of 580.9 kJ mol −1 (with both values being clearly much higher than the full-CI result of 506.6 kJ mol −1 in the calculation of Bauschlicher and Langhoff [35]). Combined with the experimentally determined value [36] of D e for Li 2 (8516.61 cm −1 ) we calculate an From the ab initio value for LiF + Li(2 2 S) production, we can compute the reaction exoergicities of all the lithium electronic states formed in the reaction and determine what is the highest electronic state formed in this reaction at 0 K. This is complicated by the narrow separation of lithium electronic states close to the ionization limit.…”

Alkali Metal Hydride Complexes: Well-Defined Molecular Species of Saline Hydrides

“…It was further suggested that the 'decamer' [Li 10 H(OtBu) 9 ] is the photochemical decomposition product and the 'dodecamer' [Li 12 H(OtBu) 11 ] is the thermal decomposition product. [69] Subsequently, the same set of studies led to the crystalline 'superaggregate' [Li 33 H 17 (OtBu) 16 ] 4 (see Fig. 5) from similar experiments with prolonged irradiation using an Hg lamp at À408C.…”

“…From these ground-and excited-state spectra, the vibrational and rotational constants of the molecules can then be approximated and other physical data such as internuclear distances can be assigned and compared with results from theoretical calculations with good agreement. [11,16] A Reported decomposition temperature, [17] reported decomposition temperature at 1 atm (,0.1 MPa) H 2 . [1] Because the alkali metal hydrides, especially LiH, are very small and simple ionic solids or diatomic molecules, a large number of theoretical studies have investigated numerous compositions and properties of these systems, including stoichiometric (LiH) n , hydrogen-rich or Li-rich clusters or phases that are beyond the scope of this report, but selected examples have been included throughout this article and often accompany experimental studies.…”

Reaction Kinetics of Meteoric Sodium Reservoirs in the Upper Atmosphere

“…S4, the modelled rate constants are very sensitive to this parameter, as well as to the high pressure limit rate constant assumed. 44,45 Two recent ab initio studies at CCSD(T)//CBS 68 …”