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Correct virial formulation in the isotropic periodic sum method

J. Chem. Phys. 131, 164103 (2009); doi:10.1063/1.3247876

Published 22 October 2009

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Iordan H. Hristov,1 Reginald Paul,1 and Stephen J. Paddison2
1Department of Chemistry, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada
2Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
The original formulation of the virial in the isotropic periodic sum (IPS) method assumes that the sphere defining the local region has a constant radius (the cutoff) independent of the system size. This assumption neglects a virial term originating from the separation between the local sphere and its periodic images. When comparing the IPS virial with that calculated from the cutoff plus long range correction method, the difference observed can be erroneously attributed to the representation of the infinite region. We show that when the two virials are calculated consistently the observed difference is significantly reduced. Additionally, the correct virial that includes the previously missing term is much simpler to calculate. We prove that in the IPS method the virial can be obtained as n/3 times the potential energy for the case of 1/rn type potentials. ©2009 American Institute of Physics
History: Received 26 February 2009; accepted 23 September 2009; published 22 October 2009
Permalink: http://link.aip.org/link/?JCPSA6/131/164103/1
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KEYWORDS and PACS

Keywords
PACS
  • 31.50.-x
    Potential energy surfaces (atoms and molecules)
  • 31.10.+z
    Theory of electronic structure, electronic transitions, and chemical binding in atoms and molecules
  • YEAR: 2009

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ISSN:
0021-9606 (print)   1089-7690 (online)
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REFERENCES (17)
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  4. A more explicit notation was used in Ref. 1. For the potential designated there as epsilonij (rij) we use 1/rn. Our Ulocal corresponds to (1/2)[summation]rj[is-an-element-of]Omegaiepsilon(rij) and Uperiodic to (1/2)[summation]rj[is-an-element-of]Omegaiphi(rij,Omegai).
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