Car-Parrinello density matrix search with a first principles fictitious electron mass method for electronic wave function optimization.

In spite of its success in molecular dynamics and the advantage of being a first order propagation technique, the Car-Parrinello method and its variations have not been successful in self-consistent-field (SCF) wave function optimization due to slow convergence. In this article, we introduce a first principles fictitious mass scheme to weigh each individual density element differently and instantaneously. As an alternative to diagonalization in SCF, the Car-Parrinello scheme is implemented as a density matrix search method. Not only does the fictitious mass scheme developed herein allow a very fast SCF convergence, but also the Car-Parrinello density matrix search (CP-DMS) exhibits linear scaling with respect to the system size for alanine helical chain test molecules. The excellent performance of CP-DMS holds even for very challenging compact three-dimensional quantum particles. While the conventional diagonalization based SCF method has difficulties optimizing electronic wave functions for CdSe quantum dots, CP-DMS shows both smooth and faster convergence.