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SUMMARY:CCQ Seminar: Fabian Pavošević
DTSTART:20201110T150000Z
DTEND:20201110T160000Z
DTSTAMP:20260907T002400Z
UID:indico-event-1010@indico.flatironinstitute.org
DESCRIPTION:Multicomponent coupled cluster methods for combining electroni
 c and nuclear quantum effects\n\n\nAn accurate description of multicompone
 nt systems\, in which more than one type of particle is described quantum 
 mechanically\, is an important yet challenging task for quantum chemistry.
  The most essential example of a multicomponent system is a molecule where
  both electrons and nuclei are treated quantum mechanically beyond the Bor
 n-Oppenheimer approximation. Among different approaches for achieving that
  goal\, the nuclear-electronic orbital (NEO) method1 provides a framework 
 for the accurate and efficient description of multicomponent systems. In t
 he NEO approach\, select nuclei\, in addition to all electrons\, are treat
 ed quantum mechanically with molecular orbital techniques\, including nucl
 ear quantum\neffects such as proton delocalization\, anharmonicity\, and z
 ero-point energy directly into energy calculations and geometry optimizati
 ons. The simplest method that can be formulated in the NEO framework is Ha
 rtree-Fock (NEO-HF).1 However\, due to the lack of inclusion of correlatio
 n effects between quantum particles (i.e.\, electron-electron\, proton-pro
 ton and electron-proton)\, NEO-HF delivers a poor performance for the calc
 ulation of properties such as energies and proton densities.\nThis talk wi
 ll present the development and efficient implementation of various coupled
  cluster\nbased methods within the NEO framework for the calculation of nu
 clear quantum effects of molecules. We will start by discussing an efficie
 nt implementation of the coupled cluster singles and doubles method within
  the NEO framework (NEO-CCSD).2 Because inclusion of single excitations in
  the NEO-CCSD method is shown to play a crucial role in the level of accur
 acy\, the multicomponent orbital optimized NEO-CCD approaches will also be
  discussed (NEO-OOCCD). The NEO-OOCCD method can be approximated to give o
 rbital optimized second-order Møller-Plesset NEO-OOMP2 method or scaled-o
 pposite-spin version of the NEO-OOMP2.3 The implemented methods were then 
 employed to calculate proton affinities that were benchmarked against both
  experimentally determined values\, as well as to calculate other molecula
 r properties such as proton densities.2\, 4 To allow calculation of the ex
 cited electronic and proton vibrational states\, as well as excited mixed 
 electron-proton vibronic states\, the multicomponent equation-of-motion co
 upled cluster with singles and doubles (NEO-EOM-CCSD) method is presented.
 5\, 6\n\nhttps://indico.flatironinstitute.org/event/1010/
URL:https://indico.flatironinstitute.org/event/1010/
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