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Updated: Jun 22, 2026

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Energy gradients in combined fragment molecular orbital and polarizable continuum model (FMO/PCM) calculation
Hui Li1, Dmitri G Fedorov, Takeshi Nagata
1Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA. hli4@unl.edu
Abstract:
The analytic energy gradients for the combined fragment molecular orbital and polarizable continuum model (FMO/PCM) method are derived and implemented. Applications of FMO/PCM geometry optimization to polyalanine show that the structures obtained with the FMO/PCM method are very close to those obtained with the corresponding full ab initio PCM methods. FMO/PCM (RHF/6-31G* level) is used to optimize the solution structure of the 304-atom Trp-cage miniprotein and the result is in agreement with NMR experiments. The key factors determining the relative stability of the alpha-helix, beta-turn and the extended form in solution are elucidated for polyalanine.
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