Simulated annealing to locate various stationary points in semiempirical methods

Abstract

In this work, an algorithm was developed to study the potential energy surfaces in the coordinate spaces of molecules by a nonlocal way, in contrast to classic energy minimizers as the BFGS or the DFP method. This algorithm, based on the specificities of semiempirical methods, mixes simulated annealing and local searches to reduce computation costs. By this technique, the global energy minimum can be localized. Moreover, local minima that are close in energy to the global minimum are also obtained. If the search is not only for minima but for all stationary points (minima, saddle points.. . ), then the energy is replaced by the gradient norm, which reaches its minimum values at stationary points. The annealing process is stopped before having accurately reached the global minimum and generates a list of geometries whose energies (respectively, whose gradients) are optimized by local minimizers. This list of geometries is shortened from the nearly equivalent geometries by a dynamic single-clustering analysis. The energy/gradient local minimizers act on the clustered list to produce a set of minimahtationary points. A targeted search of these points and reduction of the costs are reached by the way of several penalty functions. They eliminatewithout energy calculation-most of the points generated by random walks on the potential energy surface. These penalty functions (on the total moment of inertia or on interatomic distances) are specific to the class of problem studied. They account for the nonrupture of either specific chemical bonds or rings in cyclic molecules, they assure that molecular systems are kept bonded, and they avoid the collapsing of atoms. 0 1992 John Wiley & Sons, Inc.

How stereochemistry influences the taste of wine: Isolation, characterization and sensory evaluation of lyoniresinol stereoisomers

“…This involved exploring the entire conformational energy surface of the (8R,8'R,7'S)-enantiomer (1a) and carrying out semiempirical RM1 [22] calculations with the simulated annealing technique [23], as both All spectroscopic data concerning 1a, 1b and 2 are available in Supplementary material.…”

Controlling the optical properties of a conjugated co-polymer through variation of backbone isomerism and the introduction of carbon nanotubes

“…The AMPAC package was employed in all calculations [32]. Energy based simulated annealing [33] was coupled to the semiempirical Hartree-Fock Austin Model 1 (AM1) formalism [34] to locate minima on the potential energy surface. The geometry of the lowest energy minimum was then further optimised with greater precision.…”

Structures and energies of ArnH2O (n = 1–26) clusters using a nonrigid potential surface: A molecular dynamics simulation

“…Several numerical methods, such as genetic algorithms [4,5], the basin hopping and the simulated annealing approaches [6,7], and molecular dynamics simulations [8,9], have been used for determining structures, growing mechanisms and global minima of potential surfaces. Also, different coordinates systems can be used for the search procedure in these methods [10,11].…”