Derivation and Implementation of the Gradient of the R–7 Dispersion Interaction in the Effective Fragment Potential Method
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).
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The Department of Chemistry was founded in 1880.
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1880-present
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- College of Liberal Arts and Sciences (parent college)
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Abstract
The dispersion interaction energy may be expressed as a sum over R–n terms, with n ≥ 6. Most implementations of the dispersion interaction in model potentials are terminated at n = 6. Those implementations that do include higher order contributions commonly only include even power terms, despite the fact that odd power terms can be important. Because the effective fragment potential (EFP) method contains no empirically fitted parameters, the EFP method provides a useful vehicle for examining the importance of the leading R–7 odd power term in the dispersion expansion. To fully evaluate the importance of the R–7 contribution to the dispersion energy, it is important to have analytic energy first derivatives for all terms. In the present work, the gradients of the term E7 ∼ R–7 are derived analytically, implemented in the GAMESS software package, and evaluated relative to other terms in the dispersion expansion and relative to the total EFP interaction energy. Periodic boundary conditions in the minimum image convention are also implemented. A more accurate dispersion energy contribution can now be obtained during molecular dynamics simulations.
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Reprinted (adapted) with permission from The Journal of Physical Chemistry A, 120(4); 639-647. Doi: 10.1021/acs.jpca.5b11042. Copyright 2016 American Chemical Society.