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Accurate quantum chemical calculationsAn important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
Document ID
19900019364
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Bauschlicher, Charles W., Jr.
(NASA Ames Research Center Moffett Field, CA., United States)
Langhoff, Stephen R.
(NASA Ames Research Center Moffett Field, CA., United States)
Taylor, Peter R.
(Eloret Corp. Sunnyvale, CA., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1989
Subject Category
Inorganic And Physical Chemistry
Report/Patent Number
NAS 1.15:101932
NASA-TM-101932
Accession Number
90N28680
Funding Number(s)
CONTRACT_GRANT: NCC2-371
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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