ISSN:
0020-7608
Keywords:
ionization potentials
;
electron propagator
;
MCSTEP
;
NH2
;
Green's function
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
With electron propagator methods, vertical ionization potentials (IPs) and electron affinities can be calculated directly. Our implementation, known as the multiconfigurational spin tensor electron propagator method (MCSTEP), is specifically designed for open-shell and highly correlated initial states. The initial state that is usually used in MCSTEP is a complete active space (CAS) MCSCF state. We have previously demonstrated that a small balanced CAS is the optimal choice for the MCSTEP initial state. In this article, we examine two ways of determining this balanced CAS for the MCSTEP initial state. With these choices, we calculate the low-lying vertical MCSTEP IPs of NH2 and compare them with experiment for the three lowest IPs. With (aug-)cc-pVTZ, (aug-)cc-pVQZ, and extrapolated complete basis set limits, the MCSTEP IPs for both CAS choices are in very good agreement with experiment. We also calculate the next two vertical IPs where no accurate experimental estimates are as yet available. The “SCF-balanced” CAS choice is advantageous to use with MCSTEP because of simplicity, while the “SDCI-balanced” CAS is appropriate for use with MCSTEP when the initial MCSCF has undesired properties. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 729-736, 1998
Additional Material:
3 Tab.
Type of Medium:
Electronic Resource
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