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# Pople Basis Sets

i) STO-3G [1] available for H to Cl

This is the well-known minimal basis set developed by Pople and coworkers in the early 1970s. Available are in the GENBAS file the sets for H to Cl, though in the literature also STO-3G sets for third-row and fourth-row main group elements as well as some transition metal elements have been reported.

The STO-3G basis is now more or less obsolete. Its use cannot be recommended for other than testing and rough preliminary investigations.

ii) 3-21G [2] available for H to Cl

This is a small "split-valence" basis set developed by Pople and coworkers. It uses a minimal (single-zeta) description for the core orbitals and a double-zeta description for the valence orbitals.

iii) 4-31G [3] available for H to Cl

The 4-31G set is similar to the 3-21G set, except that more primitive Gaussian functions are used.

iv) 6-31G [4] available for H to Cl

This is yet another split-valence set employing still more primitive Gaussians. Available for elements H to Cl.

v) 6-311G [5]

This is a split-valence set with a triple-zeta description of the valence orbtals and a minimal basis-set description of the core orbitals. Sets are available for H to Ne. It has been claimed in the literature [6-311g2] that this basis set is not really of triple-zeta valence quality.

vi) 6-31G* [6] available for H to Cl

This is the 6-31G basis supplemented with $d$ polarization function on all atoms except H and He. Note that this basis employs Cartesian polarization functions and should be used with SPHERICAL=OFF. The polarization exponents are Li (0.2); Be (0.4); B (0.6); C-Ne (0.8); Na, Mg (0.175); Al (0.325); Si (0.45); P (0.55); S (0.65); Cl (0.75).

vii) 6-31G** [7] available for H to Cl

The same as the 6-31G* basis except that the sets for H and He are supplemented by $p$ functions. The used exponents for H and He are 1.1.

viii) 6-311G* [8] available for H to Ne

This is the 6-311G basis supplemented with $d$ polarization functions on all atoms except H and He. Note that this basis has been especially developed for correlated calculations and (unlike 6-31G*) employs spherical polarization functions. The used polarization exponents are Li (0.2); Be (0.401); C (0.626); N (0.913); O (1.292); F (1.75); Ne (2.304)

ix) 6-311G** [9] available for H to Ne

The same as 6-311G* except that the sets for H and he are supplemented by $p$ functions. The used exponents for H and He are 0.75.

x) 6-31++G* and 6-31++G** [10]

References

[1] W.J.Hehre, R.F.Stewart, and J.A.Pople, J. Chem. Phys. 51, 2657 (1969) (for first-row elements);
W.J.Hehre, R.Ditchfield, R.F.Stewart, and J.A.Pople,J.Chem. Phys. 52, 2769 (1970) (for second-row elements and improved scale factors for Li and Be);
W.J.Pietro, B.A.Levi, W.J.Hehre, and R.F.Stewart, Inorg.Chem. 19, 2225 (1980)(for third-row elements).

[2] J.S. Binkley, J.A. Pople, and W.J. Hehre, J. Am. Chem. Soc. 102, 939 (1980) (first-row elements)
M.S. Gordon, J.S. Binkley, J.A. Pople, W.J. Pietro, and W.J. Hehre, J. Am. Chem. Soc. 104, 2797 (1982) (second-row elements)

#431g [3]

#6-311g [9] R. Krishnan, J.S. Binkley, R. Seeger, and J.A. Pople, J. Chem. Phys. 72, 650 (1980); for first-row elements