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Title: Low-rank decomposition of potential energy surfaces for rovibrational properties at high energies.


Abstract not provided.

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Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Proposed for presentation at the Symposium.
Country of Publication:
United States

Citation Formats

Heindel, Joseph, Rai, Prashant, Jasper, Ahren, Sargsyan, Khachik, and Najm, Habib N. Low-rank decomposition of potential energy surfaces for rovibrational properties at high energies.. United States: N. p., 2016. Web.
Heindel, Joseph, Rai, Prashant, Jasper, Ahren, Sargsyan, Khachik, & Najm, Habib N. Low-rank decomposition of potential energy surfaces for rovibrational properties at high energies.. United States.
Heindel, Joseph, Rai, Prashant, Jasper, Ahren, Sargsyan, Khachik, and Najm, Habib N. 2016. "Low-rank decomposition of potential energy surfaces for rovibrational properties at high energies.". United States. doi:.
title = {Low-rank decomposition of potential energy surfaces for rovibrational properties at high energies.},
author = {Heindel, Joseph and Rai, Prashant and Jasper, Ahren and Sargsyan, Khachik and Najm, Habib N.},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7

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  • Here, a new method is proposed for a fast evaluation of high-dimensional integrals of potential energy surfaces (PES) that arise in many areas of quantum dynamics. It decomposes a PES into a canonical low-rank tensor format, reducing its integral into a relatively short sum of products of low-dimensional integrals. The decomposition is achieved by the alternating least squares (ALS) algorithm, requiring only a small number of single-point energy evaluations. Therefore, it eradicates a force-constant evaluation as the hotspot of many quantum dynamics simulations and also possibly lifts the curse of dimensionality. This general method is applied to the anharmonic vibrationalmore » zero-point and transition energy calculations of molecules using the second-order diagrammatic vibrational many-body Green's function (XVH2) theory with a harmonic-approximation reference. In this application, high dimensional PES and Green's functions are both subjected to a low-rank decomposition. Evaluating the molecular integrals over a low-rank PES and Green's functions as sums of low-dimensional integrals using the Gauss–Hermite quadrature, this canonical-tensor-decomposition-based XVH2 (CT-XVH2) achieves an accuracy of 0.1 cm -1 or higher and nearly an order of magnitude speedup as compared with the original algorithm using force constants for water and formaldehyde.« less
  • In this report, results are presented for continuum electrostatic calculations of proteins and DNA (up to 10,000 atoms) in which the solute charge density is treated fully quantum-mechanically at the semi-empirical level using recently developed linear-scaling electronic structure methods. In this way, the contribution of solute polarization to the salvation free energy and electrostatic potential surfaces is directly assessed. Results indicate that for proteins this contribution is typically 10-20% of the total salvation free energy, and for DNA is around 2-5%. More importantly, solute polarization can have a considerable local affect on the electrostatic potential surface in highly polar regionsmore » such as protein active sites where there is a large degree of charge-charge interaction. The methodology presented provides a foundation for a host of applications to the quantum mechanical study of macromolecules in solution.« less
  • The relative energies of the stationary points on the FH/sub 2/ and H/sub 2/CO nuclear potential energy surfaces relevant to the hydrogen atom abstraction, H/sub 2/ elimination and 1,2-hydrogen shift reactions have been examined using fourth-order Moller--Plesset perturbation theory and a variety of basis sets. The theoretical absolute zero activation energy for the F+H/sub 2/..-->..FH+H reaction is in better agreement with experiment than previous theoretical studies, and part of the disagreement between earlier theoretical calculations and experiment is found to result from the use of assumed rather than calculated zero-point vibrational energies. The fourth-order reaction energy for the elimination ofmore » hydrogen from formaldehyde is within 2 kcal mol/sup -1/ of the experimental value using the largest basis set considered. The qualitative features of the H/sub 2/CO surface are unchanged by expansion of the basis set beyond the polarized triple-zeta level, but diffuse functions and several sets of polarization functions are found to be necessary for quantitative accuracy in predicted reaction and activation energies. Basis sets and levels of perturbation theory which represent good compromises between computational efficiency and accuracy are recommended.« less
  • A theoretical study of two of the low-lying NH/sub 2//sup +/ potential energy surfaces was performed. The intersection and avoided intersection (for C/sub s/ geometries) of the lowest /sup 3/A/sub 2/ and /sup 3/B/sub 1/ surfaces allows a pathway by which the ground state of HH/sub 2//sup +/ may be accessed without a potential barrier. The electronic structure calculations employed a double zeta plus polarization basis set, and correlation effects were taken into account using the newly developed Vector Method (VM). To test the validity of this basis, additional self-consistent-field studies were performed using a very large contracted gaussian basismore » N(13s 8p 3d/9s 6p 3d), H(6s 2p/4s 2p). The /sup 3/A/sub 2/ surface, on which N/sup +/ and H/sub 2/ may approach, has a surprising deep potential minimum, approximately 60 kcal/mole, occurring at r/sub e/(NH) approximately 1.26 A and theta/sub e/(HNH) approximately 43/sup 0/. Electron correlation is responsible for about 15 kcal of this well depth, which appears fairly insensitive to extension of the basis set beyond the double zeta plus polarization level. The line of intersection (or seam) of the /sup 3/A/sub 2/ and /sup 3/B/sub 1/ surfaces is presented both numerically and pictorially. The minimum energy along this seam occurs at approximately 51 kcal below separated N/sup +/ + H/sub 2/. Thus for sufficiently low energies one expects N/sup +/ - H/sub 2/ collisions to provide considerable ''complex formation.'' 3 figs, 1 table, 28 refs.« less
  • JPL's concept for producing fuels from peat, lignite, and subbituminous coals pyrolyzes wet feed in a solar reactor using a high-temperature heat-transfer fluid as the reaction medium. Laboratory studies have so far examined the rapid pyrolysis of neat feed materials at various temperatures, heating rates, and residence times, with different catalysts, and with and without the heat-transfer fluid. Researchers will apply the resulting data to the design of bench-scale apparatus for wet-pyrolysis tests.