Basis set, for molecular orbitals

S. Huzinaga, J. Andzelm, and M. Klobukowski, Gaussian Basis Sets for Molecular Orbital Calculations, Elsevier, Amsterdam, The Netherlands, 1984. 

Multicenter Basis Set for Molecular Orbital Calculations Applications to FeCl. ... 

Applying a variational procedure, defining a basis set for molecular orbitals and using standard approximations, one is able to obtain a matrix equation with the standard Hartree-Fock or Kohn-Sham form [100], which however also contains terms dependent on the metal-molecule interaction... 

As is apparent from the above definitions, each of these effective matrices depend on basis sets and molecular orbitals of both fragments. It is also important to observe that these matrices possess a correct asymptotic behavior as at large interfragment distances they become the usual overlap and Fock matrices of the separate fragments, while the paired secular systems uncouple and converge to the separate Roothaan equations for the single monomers. Finally, as it is usual in a supermolecular approach, the interaction energy is expressed as... 

Although calculation of SCF wave functions for closed-shell, reasonably small molecules is essentially a routine procedure, molecular Cl calculations often present special problems. To obtain reliable results, one must use sound judgment in choosing the basis set, the molecular orbitals, the configuration functions to be included, and the procedure to be used. 

P. J. Hay, J. Chem. Phys., 66, 4377 (1977). Gaussian Basis Sets for Molecular Calculations. The Representation of 3d Orbitals in Transition Metal Atoms. 

P. J. Hay, Gaussian basis sets for molecular calculations. The representation of 3d orbitals in transition-metal atoms, J. 

Flehre W J, Ditchfieid R and Popie J A 1972 Self-consistent molecular-orbital methods XII. Further extension of Gaussian-type basis sets for use in molecular orbital studies of organic molecules J. Chem. Phys. 56 2257-61 Flariharan P C and Popie J A 1973 The influence of polarization functions on molecular orbital hydrogenation energies Theoret. Chim. Acta. 28 213-22... 

Krishnan R, Binkley J S, Seeger R and Popie J A 1980 Self-consistent molecular orbital methods XX. A basis set for correlated wave functions J. Chem. Phys. 72 650-4... 

To solve the Kohn-Sham equations a number of different approaches and strategies have been proposed. One important way in which these can differ is in the choice of basis set for expanding the Kohn-Sham orbitals. In most (but not all) DPT programs for calculating the properties of molecular systems (rather than for solid-state materials) the Kohn-Sham orbitals are expressed as a linear combination of atomic-centred basis functions ... 

A very important difference between H2 and molecular orbital calculations is electron correlation. Election correlation is the term used to describe interactions between elections in the same molecule. In the hydrogen molecule ion, there is only one election, so there can be no election correlation. The designators given to the calculations in Table 10-1 indicate first an electron correlation method and second a basis set, for example, MP2/6-31 G(d,p) designates a Moeller-Plesset electron coiTclation extension beyond the Hartiee-Fock limit canied out with a 6-31G(d,p) basis set. 

Binkley, J.S. Pople, J.A. Hehre, W.J. Self-consistent molecular orbital methods. 21. Small split-valence basis sets for first-row elements J. Am. Chem. Soc. 102 939-947, 1980. 

You can use multiple basis sets in a single molecular system. The Apply Basis Set in HyperChem applies the currently selected basis set to the selected atoms or to all the atoms in HyperChem if there is no current selection. For example, some heavy atoms might have a 6-3IG basis set (s and p only) while other heavy atoms might use a 6-3IG basis set (with d-orbitals). This is an unusual but flexible option for ab initio calculations. 

Ab initio methods are characterized by the introduction of an arbitrary basis set for expanding the molecular orbitals and then the explicit calculation of all required integrals involving this basis set. 

Feller, D., Davidson, E. R., 1990, Basis Sets for Ab Initio Molecular Orbital Calculations and Intermolecular Interactions , Rev. Comput. Chem., 1, 1. 

Hehre, W. J., Ditchfield, R., Pople, J. A., 1972, Self-Consistent Molecular Orbital Methods. XII. Further Extensions of Gaussian-Type Basis Sets for Use in Molecular Orbital Studies of Organic Molecules J. Chem. Phys., 56, 2257. 

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