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The effect of disconnected wavefunction clusters of double excitations on the correlation energy of molecules

✍ Scribed by Ivan Hubač; Miroslav Urban; Vladimír Kellö

Publisher
Elsevier Science
Year
1979
Tongue
English
Weight
413 KB
Volume
62
Category
Article
ISSN
0009-2614

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✦ Synopsis

Recehrd 31 Octooer 197E;in tinal form IS Deccmbcr I978 The eftkct at'quz~drupiy exited contigurations throu$i the fourth order of MB RSPT on the correlation energy of molrcules is studied-The correlation energy of the BH, Hz0 and X2 moIecuIes is c&x&ted in such a way that the second pIus third order ofJiB RSPT are inch&d fully. and from the fourth order of MB RSPT only thaws dkwams are mcluded x*hich corrrspond to quadruply cwited configurations. This correlation energy is compared xsith that obtained by CI calculations indud%< quadrupb ewitcd confi,umtions. Taco effects can be studied by these calctdations, namcIy_ the size inconsistency term in CL x well as the net quadruple cxitation cffcct, i.e. the further Iortering of the correlation energy by qusdruply e&ted confqurations.

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