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Selection of the reduced virtual space for correlated calculations. An application to the energy and dipole moment of H2O

✍ Scribed by Carlos Sosa; Jan Geertsen; Gary W. Trucks; Rodney J. Bartlett; James A. Franz

Publisher
Elsevier Science
Year
1989
Tongue
English
Weight
650 KB
Volume
159
Category
Article
ISSN
0009-2614

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✦ Synopsis

Many-body perturbation theory and coupled-cluster calculations for the energy and dipole moment of Hz0 are performed using different techniques to reduce the virtual space. The optimized virtual orbital space (OVOS) method is compared with frozen natural orbitals (FNO), defined from a relaxed density matrix, and just SCF orbitals to generate an optimized reduced virtual space. It is shown that OVOS as well as FNO orbitals recover more than 9096 of the correlated energy even when the virtual space has been reduced by almost 60%. In the full occupied space, the OVOS method is slightly preferable to FNO results in intermediate sized virtual spaces. By eliminating core correlations effectively perfect agreement is found between the FNO orbitals and OVOS.

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