Pressure Annealing as a Complement to Temperature Annealing To Find Low-Energy Structures of Oligomeric Molecules

Finding the lowest-energy geometry of a molecule or collection of molecules is a fundamental challenge of modern computational chemistry and is closely related to the more general problem of optimizing a function. Temperature annealing, popularly called simulated annealing, is a powerful and commonly used technique, but it is not well suited to conformational sampling of long, oligomeric molecules. A method is presented herein that incorporates pressure as an optimization parameter to complement temperature annealing, and several tests of its effectiveness are described. Bayesian statistical analysis shows that pressure-temperature annealing confers no advantage in control simulations of Lennard-Jones particles, but it yields lower-energy structures than pure temperature annealing with significant credibility for two model polyethers, monoglyme (CH3OCH2CH2OCH3) and tetraglyme [CH3(OCH2CH2)4OCH3].