Theoretical computation of low‐lying electronic states of HCNS: A CASPT2 study

Abstract

Complete active space self-consistent field (CASSCF) and complete active space second-order perturbation theory (CASPT2) calculations in conjunction with the aug-cc-pVTZ basis set have been used to investigate the low-lying electronic states of thiofulminic acid (HCNS), HCNS þ , and HCNS À . The result of geometry optimization using CASPT2/ aug-cc-pVTZ shows that theoretically determined geometric parameters and harmonic vibrational frequencies for the HCNS ground state X 1 R þ (X 1 A 0 ) are in agreement with previous studies. The ionization energies, the electron affinity energies, the adiabatic excitation energies, and vertical excitation energies have been calculated and the corresponding cation and anion states are identified. By calculating adiabatic electron affinity, the states of HCNS À have been identified to contain both p orbital states (X 2 A 0 and 1 2 A 00 ) and dipole-bond states (1 4 A 0 and 1 4 A 00 ).

Matrix Isolation and Computational Study of the [H, C, N, Se] Isomers

“…The global PES of the analogous sulfur system, [H, C, N, S], was computationally investigated by Wierzejewska and Moc, and there are also detailed computations on the physical and spectroscopic properties of the individual isomers. , The lowest lying singlet PES of [H, C, N, S] is very similar to that of the singlet [H, C, N, O] system, i.e., four low-energy (HNCS, HCNS, HSCN, and HSNC) and two higher-energy open-chain (HNSC and HCSN) and three cyclic (HC(NS), HN(SC), and HS(CN)) singlet isomers were found. In contrast to this, the triplet PESs of the two systems are quite different; for [H, C, N, S], eight structures were identified.…”