Authors: Gary S Kedziora Stephen A Barr Rajiv Berry James C Moller Timothy D Breitzman
Publish Date: 2016/03/02
Volume: 135, Issue: 3, Pages: 79-
Abstract
Several quantum chemistry methods were compared for modeling the breaking of bonds in small molecules subjected to extreme strain This provides a rigorous test of quantum mechanical methods because a high degree of dynamical and nondynamical correlation is required to accurately model bond breaking in a strained molecule The methods tested included multireference methods unrestricted Kohn–Sham density functional theory DFT using several functionals and unrestricted coupledcluster singles and doubles It is challenging to employ the multireference method in a balanced way for the molecules considered due to the computational cost While the DFT methods are less costly and provide balanced correlation they do not have enough static correlation to properly model the bondbreaking curve to dissociation Despite this for the N12 DFT method the artifacts due to spin contamination of the unrestricted Kohn–Sham method were the least severe and tolerable Given this and the low computational cost the N12 method was chosen for subsequent dynamical simulations for modeling fracture inception in polymers under extreme strain The physical characteristics of the bondbreaking process are discussed as well as the influence of secondary conjugation on the processThe Air Force Office of Scientific Research under project number 14RX09COR supported the project The authors would also like to thank the DoD HPCMP’s User Productivity Enhancement Technology Transfer and Training PETTT Program Contract No GS04T09DBC0017 through Engility Corp for support and the AFRL DSRC for computer time and software support
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