Software news and updates

Abstract

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.

TURTLE – A gradient VBSCF Program Theory and Studies of Aromaticity

“…This implies parallellising over 99% of the program, since contrary to MO programs, the matrix elements, both those needed when calculating the wavefunction and those required in the SuperCI, dominate completely. In the present implementation, a speedup of 54 is obtained when using 64 processors [31]. An implementation using Global Arrays [32][33][34] is in progress.…”

“…Combining Eqs. (27), (31) and (32) the final expression for the derivative of the energy with respect to say a geometrical parameter is…”

A generalized Brillouin theorem (GBT)-like implementation to optimize Valence Bond wave function for excited states

“…[14,15] Parallel implementations are also available and they recently improved the efficiency of the codes. [16][17][18] In this paper, we discuss convergence issues related to an optimizer for Valence Bond non-orthogonal orbitals, with a special focus on excited states. [19][20][21] The super CI optimizer that we used is based on the Generalized Brillouin theorem [21,22]The paper is organized as follows: in the section 3, some equations are reminded, our notation is introduced, and our implementation is briefly explained.…”

The application of cholesky decomposition in valence bond calculation

“…However, valence bond (VB) theory still attracts the attentions of many chemists and is considered as one of modern chemical bonding theories, because of its ability to provide intuitive insights for chemical problems . Since the 1980s, more and more ab initio VB methods and programs have been developed and widely applied to explore the nature of chemical bond …”