A local framework for calculating coupled cluster singles and doubles excitation energies (LoFEx-CCSD)

TY - JOUR

T1 - A local framework for calculating coupled cluster singles and doubles excitation energies (LoFEx-CCSD)

AU - Baudin, Pablo

AU - Bykov, Dmytro

AU - Liakh, Dmitry

AU - Ettenhuber, Patrick

AU - Kristensen, Kasper

PY - 2017/9/17

Y1 - 2017/9/17

N2 - The recently developed Local Framework for calculating Excitation energies (LoFEx) is extended to the coupled cluster singles and doubles (CCSD) model. In the new scheme, a standard CCSD excitation energy calculation is carried out within a reduced excitation orbital space (XOS), which is composed of localised molecular orbitals and natural transition orbitals determined from time-dependent Hartree–Fock theory. The presented algorithm uses a series of reduced second-order approximate coupled cluster singles and doubles (CC2) calculations to optimise the XOS in a black-box manner. This ensures that the requested CCSD excitation energies have been determined to a predefined accuracy compared to a conventional CCSD calculation. We present numerical LoFEx-CCSD results for a set of medium-sized organic molecules, which illustrate the black-box nature of the approach and the computational savings obtained for transitions that are local compared to the size of the molecule. In fact, for such local transitions, the LoFEx-CCSD scheme can be applied to molecular systems where a conventional CCSD implementation is intractable.

AB - The recently developed Local Framework for calculating Excitation energies (LoFEx) is extended to the coupled cluster singles and doubles (CCSD) model. In the new scheme, a standard CCSD excitation energy calculation is carried out within a reduced excitation orbital space (XOS), which is composed of localised molecular orbitals and natural transition orbitals determined from time-dependent Hartree–Fock theory. The presented algorithm uses a series of reduced second-order approximate coupled cluster singles and doubles (CC2) calculations to optimise the XOS in a black-box manner. This ensures that the requested CCSD excitation energies have been determined to a predefined accuracy compared to a conventional CCSD calculation. We present numerical LoFEx-CCSD results for a set of medium-sized organic molecules, which illustrate the black-box nature of the approach and the computational savings obtained for transitions that are local compared to the size of the molecule. In fact, for such local transitions, the LoFEx-CCSD scheme can be applied to molecular systems where a conventional CCSD implementation is intractable.

KW - CCSD

KW - Excitation energies

KW - coupled cluster theory

KW - large molecules

KW - local correlation

UR - http://www.scopus.com/inward/record.url?scp=85013354729&partnerID=8YFLogxK

U2 - 10.1080/00268976.2017.1290836

DO - 10.1080/00268976.2017.1290836

M3 - Journal article

SN - 0026-8976

VL - 115

SP - 2135

EP - 2144

JO - Molecular Physics

JF - Molecular Physics

IS - 17-18

ER -