XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Development of Algorithms and Computer Programs for Performing Large-Scale Energy and Dynamics Calculations for the Excited States of Molecular Systems on Graphical Processing Units
Jeffrey R. Gour, Nathan Luehr, Christine M. Isborn, Ivan S. Ufimstev, Todd J. Martinez
PULSE Institute and Department of Chemistry, Stanford University, CA 94305
SLAC National Accelerator Laboratory, Menlo Park, CA 94305
Chemical reactions on excited electronic states play a significant role in many important processes of scientific interest, including biological photoreceptors and light-triggered or light-powered molecular devices. Unfortunately, thanks to long computer times and high disk and memory requirements, the ability to study these processes for large molecular systems with ab initio methodologies is severely restricted. In order to overcome such limitations, allowing one to perform ab initio excited-state energy, property, and dynamics calculations for larger systems than previously possible, we have recently developed new implementations of the configuration interaction singles (CIS) and Tamm-Dancoff time-dependent density functional theory (TDA-TDDFT) approaches which utilize massively multi-parallel graphical processing units (GPUs) in the calculation of energies [1] and gradients.
In this presentation, some of the details of the implementations developed in this work, which are included in the development version of the TeraChem software package, will be discussed. Following the structure of the previously developed Hartree-Fock and Kohn-Sham DFT GPU implementations [1-3], these programs utilize a direct algorithm, in which the one-electron matrix elements and two-electron coulomb integrals, as well as the corresponding gradient elements, are computed on the fly using the GPU, greatly reducing the computational cost of the calculation. To illustrate the performance and speed-ups provided by these implementations, benchmark energy and geometry optimization calculations are performed for four generations of oligothiophen dendrimers as well as for photoactive yellow protein (PYP). In addition, we use these codes to perform ab initio multiple-spawning dynamics for PYP and GFP, using the reduced computational cost to investigate the effect of increasing the size of the QM region in the QM/MM calculation relative to that of previous studies.

[1] C.M. Isborn, N. Luehr, I.S. Ufimtsev, and T.J. Martinez, J. Chem. Theory Comput. Submitted.
[2] Ufimtsev, I. S.; Martinez, T. J., J. Chem. Theory Comput. 2009, 5, 1004.
[3] Ufimtsev, I. S.; Martinez, T. J., J. Chem. Theory Comput. 2009, 5, 2619.


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