VESH: A VERTICAL ENERGY SURFACE HOPPING PROCEDURE FOR DETERMINING STABLE ISOMERS OF POLYATOMIC MOLECULAR SYSTEMS

We describe a heuristic algorithmic procedure by which a large number of points of minimal energy in configuration space of a polyatomic molecular system (isomers) can be determined. Making use of the intrinsic electronic structure energy scheme of the molecular system, the procedure is initiated from an arbitrary starting configuration and progresses via successive vertical spin, and/or charge state shifts with interposed optimization steps. In this systematic way, a great manifold of stable isomers not only on the ground state potential energy surface but also on excited spin and charge state surfaces can be located. The efficiency and computational practicability of the procedure has been tested on various examples. In these cases, the global minima have been found. Results for singlet and triplet states of the system P₄ are presented in detail.