A theoretical exploration of new species on the 1[H, Se, I] potential energy surface: Energetics, structures, IR spectra, and heats of formation

New molecular species HSeI, HISe, and SeI were investigated theoretically for the first time at a high level of theory, CCSD(T). Computations were carried out with the series of correlation consistent basis sets (aug-cc-pVnZ-PP) and the results extrapolated to the complete basis set limit. Accounting for core valence correlation into the wavefunction, and of anharmonic effects on the vibrational frequencies were also explored, making the results of structural, energetic, and vibrational properties a very reliable source of data for these yet unknown species. HSeI, viewed as normal covalently bonded species, turned out to be more stable by 42.04 kcal mol(-1) than HISe. Bonding between I and Se in HISe can be rationalized as resulting from an electron pair donation from I to Se, the classical dative bond. These two species are separated by a barrier (Delta G(#)) of 52.35 kcal mol(-1). Corrections arising from spin-orbit and scalar relativistic effects were also considered in the evaluation of atomization energies. For SeI, we estimate Delta H-f values of 36.87 and 35.16 kcal mol(-1) at 0 K and 298.15 K; for HSeI, we had 18.25 and 16.72 kcal mol(-1), respectively. (C) 2017 Elsevier B.V. All rights reserved.