Dr. A. Eugene DePrince IIIAssistant Professor
PhD – University of Chicago (2009)
Research InterestHigh-quality electronic structure software is an essential component of modern chemical research, and open-source software is particularly valuable. Our primary research efforts are dedicated to the development of open-source tools for the description of electronically excited states in complex molecules and materials.
Time-dependent quantum chemistry:
Light interactions with quantum systems are usually treated computationally by time-dependent perturbation theory, and electric fields are assumed to be of low intensity. However, a much more flexible description of light-matter interactions may be obtained, albeit at an increased computational cost, through explicitly time-dependent methods in which one propagates the electronic Schrodinger equation in the presence of a time-dependent perturbation. Such methods can describe perturbations of arbitrary strength and shape, and they correctly recover properties obtained by the usual linear-response methods when considering weak perturbations. We use such real-time time-dependent methods to describe very fast electron dynamics relevant to a number of chemical phenomena including the optical control of molecular devices and the emergence of collective behavior in quantum systems.
Large-scale CASSCF methods:
The standard approach for capturing nondynamical correlation effects in quantum chemical computations is the complete active space self-consistent field (CASSCF) method. However, because the size of the underlying configuration interaction (CI) wave function expansion grows exponentially with the size of the active space, the application of CASSCF to large actives spaces is nontrivial. The treatment of large active spaces requires one to either (i) abandon CI in favor of some other wave function expansion that scales polynomially with system size or (ii) abandon the wave function altogether. Methods that employ the two-electron reduced-density matrix (2-RDM) as the central variable (instead of the wave function) facilitate the design of polynomially-scaling CASSCF. We have developed a (soon to be free and open-source!) implementation of a 2-RDM-driven CASSCF method as a plugin to the Psi4 electronic structure package. The active-space 2-RDM is obtained from a semidefinite optimization procedure, without the use of the N-electron wave function. Our CASSCF implementation is applicable to systems with active spaces as large as 50 electrons in 50 orbitals and thousands of external orbitals.
GPU quantum chemistry:
Graphics processing units (GPUs) and other coprocessors (e.g. Intel MIC) are revolutionizing high-performance scientific computing. These devices deliver a huge number of floating-point operations at much lower cost (both physical cost and power consumption) than conventional multicore CPUs. To leverage this enormous potential in some meaningful way, however, one must usually abandon legacy algorithms in favor of new ones that account for the many annoying peculiarities of GPU programming. Our group develops new implementations of high-accuracy many-body methods for use in heterogenous computing environments where a standard compute node consists of a modern multicore CPU and at least one GPU.
|J. Fosso-Tande, T.-S. Nguyen, G. Gidofalvi, and A. E. DePrince III , J. Chem. Theory Comput. 12 , 2260-2271 (2016). "Large-scale v2RDM-driven CASSCF methods"|
|D. R. Nascimento and A. E. DePrince III , J. Chem. Phys. 143 , 214104 (2015). "Modeling molecule-plasmon interactions using quantized radiation fields within time-dependent electronic structure theory"|
|J. Fosso-Tande, D. R. Nascimento, and A. E. DePrince, III , Mol. Phys. 114 423-430 (2015). "Accuracy of two-particle N-representability conditions for describing different spin states and the singlet-triplet gap in the linear acene series"|
|D. B. Jeffcoat and A. E. DePrince III , J. Chem. Phys. 141 , 214104 (2014). "N-representability-driven reconstruction of the two-electron reduced-density matrix for a real-time time-dependent electronic structure method"|
|D. R. Nascimento and A. E. DePrince III , J. Chem. Theory Comput. 10 , 4324 (2014). "A parametrized coupled-pair functional for molecular interactions: PCPF-MI"|