Dr. Bernardo de Souza
Although mostly neglected for a very long time in Computational Chemistry, the conformational sampling of flexible molecules plays a major role in most real-life problems. The question of whether a certain guess conformer drawn or automatically generated from a plain 2D Lewis structure is the minimum on its PES is not of minor importance, because different conformers can have drastically different characteristics. From the most complicated as Circular Dichroism to simpler as the molecule’s dipole, these properties will be affected by geometry, and having a full picture of the molecular ensemble in the gas phase or solution is of importance for most of chemistry.
In this talk, we will go over some interesting cases to highlight this point, and also present the new Global Optimizer Algorithm (GOAT), implemented on the ORCA software. It is based on the ideas of Wales and Goedecker for basis-hopping and minima-hopping and can find whole ensembles, global minima and even compute conformational Entropy and Gibb’s Free energy. The GOAT can run in reasonable time with any method in ORCA with a gradient (HF, MP2, all DFT, broken-symmetry, excited states, etc) and is very efficiently parallelized. I hope to make a point and prove that this is a problem that can not continue to be neglected!
Keywords: Conformational search, global optimization, entropy, Gibb's free energy, intermolecular interactions