We are developing a modern framework for quantum based molecular dynamics simulations that combines some of the best features of regular Born-Oppenheimer and Car-Parrinello molecular dynamics. The new framework is based on an extended Lagrangian formulation of Born-Oppenheimer molecular dynamics that allows, for the first time, efficient energy conserving Born-Oppenheimer molecular dynamics simulations with a computational complexity that scales only linearly with the system size. Often only a single diagonalization per time step is required, reducing the cost by an order of magnitude compared to regular Born-Oppenheimer molecular dynamics simulations. The efficiency and accuracy of the new dynamics can be understood from a backward analysis. Instead of integrating an underlying exact dynamics with approximate forces, exact forces that do not rely on the fulfillment of the Hellmann-Feynman theorem are used to integrate the equations of motion for an approximate shadow Hamiltonian. In this way properties such as the total energy can be controlled. This geometric approach to integration is widely used in classical molecular dynamics, e.g. in the velocity Verlet algorithm. Our new framework allows this geometric technique to be applied also to self-consistent field theory. Extended Lagrangian Born-Oppenheimer molecular dynamics represents a general approach that can be applied to a broad variety of quantum based molecular dynamics applications. [Refs: A.M.N. Niklasson and M. J. Cawkwell J. Chem. Phys. 141, 164123 (2014); P. Souvatzis and A.M.N. Niklasson J. Chem. Phys. 139, 214102 (2013); M. J. Cawkwell and A.M.N. Niklasson J. Chem. Phys. 137, 134105 (2012); A.M.N. Niklasson Phys. Rev. Lett. 100, 123004 (2008)]

New generation, quantum-based molecular dynamics

251st National Meeting (2016)

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