02044nas a2200229   4500008004100000022001400041245016300055210006900218260009200287300001400379490000800393520108200401653003301483653001501516653002301531653003901554100002701593700002701620700002001647700001601667856013101683       2015                        eng d  a0026-897600aPerturbative order analysis of the similarity transformed hamiltonian in fock-space coupled cluster theory: difference energy and electric response properties0 aPerturbative order analysis of the similarity transformed hamilt  a4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcJUL  a2046-20600 v1133 a<p>A perturbative analysis of the ground-state similarity transformed Hamiltonian and its effect on the various Fock-space coupled cluster (FSCC) sectors is presented through calculation of ionisation potential, electron affinity, excitation energies and response properties. Various truncation schemes of the effective Hamiltonian are presented with explicit form of the defining equations. Based on such a truncation, the approximate methods are labelled as FSCC(n), where n represents the correlation energy of the ionised, electron attached or excited states corrected at least up to nth order within coupled cluster singles and doubles scheme (CCSD). A lower scaling CC2 type of approach (abbreviated as FS-CC2) is compared against the group of FSCC(n) methods for energies. Electric response properties have been compared and contrasted for the two lower scaling methods: FSCC(2) and FS-CC2. The various truncated methods are tested for a number of small molecules. The results obtained from a range of truncated methods are compared against full FSCCSD calculations.</p>10aelectric response properties10aFock space10aperturbative order10asimilarity transformed Hamiltonian1 aBhattacharya, Debarati1 aDutta, Achintya, Kumar1 aGupta, Jitendra1 aPal, Sourav  uhttps://library.ncl.res.in/content/perturbative-order-analysis-similarity-transformed-hamiltonian-fock-space-coupled-cluster-0