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Title: Reactive Monte Carlo sampling with an ab initio potential

Abstract

Here, we present the first application of reactive Monte Carlo in a first-principles context. The algorithm samples in a modified NVT ensemble in which the volume, temperature, and total number of atoms of a given type are held fixed, but molecular composition is allowed to evolve through stochastic variation of chemical connectivity. We also discuss general features of the method, as well as techniques needed to enhance the efficiency of Boltzmann sampling. Finally, we compare the results of simulation of NH 3 to those of ab initio molecular dynamics (AIMD). Furthermore, we find that there are regions of state space for which RxMC sampling is much more efficient than AIMD due to the “rare-event” character of chemical reactions.

Authors:
 [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1340916
Alternate Identifier(s):
OSTI ID: 1250976
Report Number(s):
LA-UR-16-21006
Journal ID: ISSN 0021-9606
Grant/Contract Number:
AC52-06NA25396; LA-UR-16-21006
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 17; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Leiding, Jeff, and Coe, Joshua D. Reactive Monte Carlo sampling with an ab initio potential. United States: N. p., 2016. Web. doi:10.1063/1.4948303.
Leiding, Jeff, & Coe, Joshua D. Reactive Monte Carlo sampling with an ab initio potential. United States. doi:10.1063/1.4948303.
Leiding, Jeff, and Coe, Joshua D. Wed . "Reactive Monte Carlo sampling with an ab initio potential". United States. doi:10.1063/1.4948303. https://www.osti.gov/servlets/purl/1340916.
@article{osti_1340916,
title = {Reactive Monte Carlo sampling with an ab initio potential},
author = {Leiding, Jeff and Coe, Joshua D.},
abstractNote = {Here, we present the first application of reactive Monte Carlo in a first-principles context. The algorithm samples in a modified NVT ensemble in which the volume, temperature, and total number of atoms of a given type are held fixed, but molecular composition is allowed to evolve through stochastic variation of chemical connectivity. We also discuss general features of the method, as well as techniques needed to enhance the efficiency of Boltzmann sampling. Finally, we compare the results of simulation of NH3 to those of ab initio molecular dynamics (AIMD). Furthermore, we find that there are regions of state space for which RxMC sampling is much more efficient than AIMD due to the “rare-event” character of chemical reactions.},
doi = {10.1063/1.4948303},
journal = {Journal of Chemical Physics},
number = 17,
volume = 144,
place = {United States},
year = {Wed May 04 00:00:00 EDT 2016},
month = {Wed May 04 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
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  • We present the first application of reactive Monte Carlo in a first-principles context. The algorithm samples in a modified NVT ensemble in which the volume, temperature, and total number of atoms of a given type are held fixed, but molecular composition is allowed to evolve through stochastic variation of chemical connectivity. We discuss general features of the method, as well as techniques needed to enhance the efficiency of Boltzmann sampling. Finally, we compare the results of simulation of NH{sub 3} to those of ab initio molecular dynamics (AIMD). We find that there are regions of state space for which RxMCmore » sampling is much more efficient than AIMD due to the “rare-event” character of chemical reactions.« less
  • Cited by 1
  • We present a many-body diffusion quantum Monte Carlo (DMC) study of the bulk and defect properties of NiO. We find excellent agreement with experimental values, within 0.3%, 0.6%, and 3.5% for the lattice constant, cohesive energy, and bulk modulus, respectively. The quasiparticle bandgap was also computed, and the DMC result of 4.72 (0.17) eV compares well with the experimental value of 4.3 eV. Furthermore, DMC calculations of excited states at the L, Z, and the gamma point of the Brillouin zone reveal a flat upper valence band for NiO, in good agreement with Angle Resolved Photoemission Spectroscopy results. To studymore » defect properties, we evaluated the formation energies of the neutral and charged vacancies of oxygen and nickel in NiO. A formation energy of 7.2 (0.15) eV was found for the oxygen vacancy under oxygen rich conditions. For the Ni vacancy, we obtained a formation energy of 3.2 (0.15) eV under Ni rich conditions. Lastly, these results confirm that NiO occurs as a p-type material with the dominant intrinsic vacancy defect being Ni vacancy. (C) 2015 AIP Publishing LLC.« less
  • Here we perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N = 1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F xc of the macroscopic electron gas withmore » an unprecedented accuracy of | Δ V | / | V | , | Δ F xc | / | F | xc ~ 10 $-$3. Finally, a comparison of our new data to the recent parametrization of F xc by Karasiev et al. [Phys. Rev. Lett. 112, 076403 (2014)] reveals significant deviations to the latter.« less