Structural characterization, infrared spectra, relative stability, dissociation energies and energy barrier for isomerization of new molecular species, HSeBr and HBrSe, were investigated at a high level of theory, CCSD(T)/CBS. HSeBr is predicted to be 44.95 kcal mol-1 more stable than HBrSe, with a barrier (ΔG#) for isomerization of 52.24 kcal mol-1. Due to the much smaller barrier for the reverse reaction, if formed, the less stable isomer is expected to be readily converted to HSeBr, except at cryogenic temperatures. The possibility of dissociation into atomic Se and HBr is also a likely one by a spin-orbit coupling mechanism. Heats of formation of SeBr and HSeBr were estimated to be 31.54 and 12.31 kcal mol-1, respectively, at 298.15 K. The effect of core-valence correlation on the structural parameters and harmonic frequencies was also evaluated, as well as the contribution of anharmonicity to the frequencies. Additional calculations performed with explicitly correlated wavefunctions showed promising results of fast convergence to the complete basis set (CBS) limit with relatively smaller basis sets.
[H, Se, Br] potential energy surface; structures; frequencies; heats of formation; isomerization
