Approximate molecular orbital

Pople, J.A. Beveridge, D.L. Approximate. Molecular Orbital I heory McGraw-Hill, New York. 1970. 

I nple J A and D L Beveridge, 1970. Approximate Molecular Orbital Theory. New York, McGraw-Hill. Riduirds W G and D L Cooper 1983. Ab initio Molecular Orbital Calculations for Qieniists. 2nd Edition. Oxford, Clarendon Press. 

As presented, semi-empirieal methods are based on a single-eonfiguration pieture of eleetronie strueture. Extensions of sueh approaehes to permit eonsideration of more than a single important eonfiguration have been made (for exeellent overviews, see Approximate Molecular Orbital Theory by J. A. Pople and D. E. Beveridge, McGraw-Hill, New York... 

HyperChem currently supports one first-principle method ab initio theory), one independent-electron method (extended Hiickel theory), and eight semi-empirical SCFmethods (CNDO, INDO, MINDO/3, MNDO, AMI, PM3, ZINDO/1, and ZINDO/S). This section gives sufficient details on each method to serve as an introduction to approximate molecular orbital calculations. For further details, the original papers on each method should be consulted, as well as other research literature. References appear in the following sections. 

We wish to list here the rules one may follow in combining partial orbitals, POs (AO, FO, BO) into approximate molecular orbitals. 

Pople JA, Beveridge DL (1970) Approximate Molecular Orbital Theory. McGraw Hill, New Y ork... 

Pople, J. A. Beveridge, D. L. Approximate Molecular Orbital Theory, 1st ed. McGraw-Hill New York, 1970. 

Pople JA, Beveridge DL. Approximate molecular orbital theory. New York McGraw-Hill, 1970. 

Scheme la shows the approximate molecular orbital model for the hypervalent X-E-X 3c-4e in EX4, such as SC14. Characters of the three molecular orbitals are bonding (v /i), nonbonding (v /2), and anti-bonding (v /3). Two electrons are in and two in v 2. Electrons in v 2 localize on X of X-E-X and the hypervalent bonds are mainly characterized by v 2. Consequently,... 

The hypervalent chalcogen chemistry has been developed to higher coordinated species with various ligands,7 10 where TBP changes to square pyramidal (SP) or octahedral (Oh), etc. Additional atomic orbitals of E, such as an 5-orbital, may operate to stabilize the structures.10b The concept is also extended over linear a-bonds constructed by m ( > 4) atoms with n electrons (extended hypervalent bonds mc-ne (in > 4)).11 14 The approximate molecular orbital model for mc-ne (m > 4) is also exhibited in Scheme la, exemplified by 4c-6e. 

These considerations suggest that it might be useful to approximate molecular orbitals as sums of atomic orbitals. Thus for the hydrogen molecule ion hJ, a one-electron system, one could consider a wave function - based on the exact orbitals for the separated atoms - of the form, in... 

Hartree—Fock Approximate Molecular Orbital Theory... 

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