Coupling Quantum Mechanics and Static Modes to explore the energy landscape in complex systems

Simulating the dynamics of complex systems requires the precise identification of atomic diffusions, including rare-events, through an exhaustive exploration of the energy landscape. To reduce the associated computational cost we propose to use the Static Mode (SM) method [Ref1] together with ab initio calculations (QM). SM are first calculated from the Hessian matrix associated to an initial relaxed configuration. Each SM represents the strain field of a molecular system submitted to the stress (displacement) of a given atom in a given direction. Using this information, we screen the perturbation of all atoms in all directions and evaluate the local response of the system. The most relevant deformations are then selected in regards to a criterion chosen by the user to guide the evolution of the system. Finally, from the deformed states, ab initio calculations are used to reach new minima. The QMSM method that we propose can be applied to any type of system. Its validation will be presented, based on two different applications: how DNA can graft on alumina surface and how defect can migrate in silicon bulk.

Ref1 : M. Brut et al. European Physical Journal E vol. 28,17-25 (2009)