Software news and updates

A parallel version of the valence bond program TURTLE has been developed. In this version the calculation of matrix elements is distributed over the processors. The implementation has been done using the message‐passing interface (MPI), and is, therefore, portable. The parallel version of the program is shown to be quite efficient with a speed‐up of 55 at 64 processors. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 665–672, 2001     

The electronic structure of inorganic benzenes: valence bond and ring-current descriptions

Valence bond (VB) theory and ring-current maps have been used to study the electronic structure of inorganic benzene analogues X(6)H(6) (X = C (1), Si (2)), X(6) (X = N (3), P (4)), X(3)Y(3)H(6) (X,Y = B,N (5), B,P (6), Al,N (7), Al,P (8)), and B(3)Y(3)H(3) (Y = O (9), S (10)). It is shown that the homonuclear compounds possess benzene-like character, with resonance between two Kekulé-like structures and induced diatropic ring currents. Heteronuclear compounds typically show localization of the lone pairs on the electronegative atoms; Kekulé-like structures do not contribute. Of the heteronuclear compounds, only B(3)P(3)H(6) (6) has some benzene-like features with a significant contribution of two Kekulé-like structures to its VB wave function, an appreciable resonance energy, and a discernible diatropic ring current in planar geometry. However, relaxation of 6 to the optimal nonplanar chair conformation is accompanied by the onset of localization of the ring current.