Theoretical investigation on potential energy surface of CSiNP molecule.

The structural, spectroscopic and kinetic properties of small molecules composed of second-row elements such as Si and P are vital to understanding the growing process of relevant semiconductors and functional films as well as to predicting new species to be detected in space. In this paper, a detailed computational study is performed on the singlet and triplet [C,Si,N,P] potential energy surfaces at the DFT/B3LYP, QCISD and CCSD(T) (single-point) levels. A total of 38 (15 for singlet and 23 for triplet) minimum isomers and 37 (19 for singlet and 18 for triplet) interconversion transition states are located. Generally, the triplet species lie energetically higher than the singlet ones. At the CCSD(T)/6-311G(2df)//B3LYP/6-311G(d) + ZPVE level, the lowest-lying isomer is SiNCP(1Σ) 11 (0.0 kcal/mol) followed by NCPSi(1A′) 12 (8.9), NCSiP(1Σ) 13 (19.7), PCNSi(1A′) 14 (19.8), CNSiP(1Σ) 15 (26.5), SiCNP 16(1Σ) (31.1) and CNPSi(1A′) 17 (32.2). Except for the isomer 14 with very low isomerization barrier, the remaining six ones have reasonable kinetic stabilities. In addition, although the linear isomers NSiCP 18 (63.8) and SiCPN 110 (73.5) are energetically very high-lying, they contain very large isomerization barriers to allow for existence either in laboratory or in space. By means of structural and bonding analysis, the interesting Si- or P-related triple-bonding are revealed among species like 11 (C≡P), 13 (Si≡P), 15 (Si≡P), 16 (Si≡C, N≡P). Since up to now, stable typical Si≡P and Si≡N triply-bonded species are still experimentally unknown, isomers 11, 13, 15 and 16 may represent such good examples. Moreover, the intramolecular donor–acceptor mechanism from the exocyclic π-bonding to the vacant orbital of one ring-atom is proposed to account for the unique three-membered ring-like structure of the chainlike isomers 12, 14 and 17. Finally, the similarities and discrepancies of CSiNP molecule are compared to the analogous 18-valence-electrons species AA′BB′ (A, A′ are group IV elements and B, B′ are group V elements) such as C2N2, C2NP, CSiN2, Si2N2, Si2NP, and Si2P2. [Copyright &y& Elsevier]