On the relative stabilities of the linear and triangular forms of B3N

Abstract

The two recently elucidated isomers of B3N lowest in energy, the singlet linear ((1) Sigma(+)) and triangular ((1)A(1)') structures, are studied further. The all-electron limited configuration interaction method with an single and double excitations (CISD), quadratic configuration interaction with all singles and doubles (QCISD), and with a quasiperturbative treatment of higher excitations (QCISD(T)) are used together with a number of basis sets of the Pople family. Using standard G1 theory, the total atomization energy Sigma D-0 for the linear structure is found to be 1397 Kj/mol, which means the molecule is quite stable with respect to fragmentation. The X (1) Sigma(+) state has two intense IR bands in the 1100-1200 and 2000-2100 cm-(1) ranges and should be observable; isotopic substitution data have been given. The inter-isomeric thermodynamics is described using the best computed parameters, and it is shown that even at high temperatures the triangular form should represent at most about 3% of the B3N system.