Department WebPage

Dr. A. Eugene DePrince IIIAssociate ProfessorPhD – University of Chicago (2009)


Research Interest
Highquality electronic structure software is an essential component of modern chemical research, and opensource software is particularly valuable. Our primary research efforts are dedicated to the development of opensource tools for the description of electronically excited states in complex molecules and materials.Timedependent quantum chemistry:
Light interactions with quantum systems are usually treated computationally by timedependent perturbation theory, and electric fields are assumed to be of low intensity. However, a much more flexible description of lightmatter interactions may be obtained, albeit at an increased computational cost, through explicitly timedependent methods in which one propagates the electronic Schrodinger equation in the presence of a timedependent perturbation. Such methods can describe perturbations of arbitrary strength and shape, and they correctly recover properties obtained by the usual linearresponse methods when considering weak perturbations. We use such realtime timedependent 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.
Largescale CASSCF methods:
The standard approach for capturing nondynamical correlation effects in quantum chemical computations is the complete active space selfconsistent 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 twoelectron reduceddensity matrix (2RDM) as the central variable (instead of the wave function) facilitate the design of polynomiallyscaling CASSCF. We have developed a (soon to be free and opensource!) implementation of a 2RDMdriven CASSCF method as a plugin to the Psi4 electronic structure package. The activespace 2RDM is obtained from a semidefinite optimization procedure, without the use of the Nelectron 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 highperformance scientific computing. These devices deliver a huge number of floatingpoint 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 highaccuracy manybody methods for use in heterogenous computing environments where a standard compute node consists of a modern multicore CPU and at least one GPU.
Publications
D. R. Nascimento and A. E. DePrince, III, J. Chem. Theory Comput. 14, 24182426 (2018). "Spatial and spin symmetry breaking in semidefiniteprogrammingbased HartreeFock theory" 
E. Maradzike, G. Gidofalvi, J. M. Turney, H. F. Schaefer, III, and A. E. DePrince, III, J. Chem. Theory Comput. 13, 41134122 (2017). “Analytic energy gradients for variational twoelectron reduceddensitymatrixdriven complete active space selfconsistent field theory” 
D. R. Nascimento and A. E. DePrince, III, J. Phys. Chem. Lett. 8, 29512957 (2017). "Simulation of nearedge Xray absorption fine structure with timedependent equationofmotion coupledcluster theory" 
D. R. Nascimento and A. E. DePrince, III, J. Chem. Theory Comput. 12, 58345840 (2016). "Linear absorption spectra from explicitly timedependent equationofmotion coupledcluster theory" 
A. E. DePrince, III , J. Chem. Phys. 145, 164109 (2016). "Variational optimization of the twoelectron reduceddensity matrix under purestate Nrepresentability conditions" 
J. FossoTande, T.S. Nguyen, G. Gidofalvi, and A. E. DePrince III , J. Chem. Theory Comput. 12 , 22602271 (2016). "Largescale variational twoelectron reduceddensitymatrixdriven complete active space selfconsistent field methods" 
D. R. Nascimento and A. E. DePrince III , J. Chem. Phys. 143 , 214104 (2015). "Modeling moleculeplasmon interactions using quantized radiation fields within timedependent electronic structure theory" 
J. FossoTande, D. R. Nascimento, and A. E. DePrince, III , Mol. Phys. 114 423430 (2015). "Accuracy of twoparticle Nrepresentability conditions for describing different spin states and the singlettriplet gap in the linear acene series" 
D. B. Jeffcoat and A. E. DePrince III , J. Chem. Phys. 141 , 214104 (2014). "Nrepresentabilitydriven reconstruction of the twoelectron reduceddensity matrix for a realtime timedependent electronic structure method" 
D. R. Nascimento and A. E. DePrince III , J. Chem. Theory Comput. 10 , 4324 (2014). "A parametrized coupledpair functional for molecular interactions: PCPFMI" 