8.2.1 Overview

Q-Chem is equipped with many standard basis sets,^{11, B. P. Pritchard, D. Altarawy, B. Didier, T. D. Gibson, and T. L. Windus (2019)} and allows the user to specify the required basis set by its standard symbolic representation. The available built-in basis sets include the following types:

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  Pople basis sets^{110, 385, 281, 282, 283, 373}

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  Dunning basis sets²⁹³

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  Correlation-consistent (cc) Dunning basis sets, including:

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    Standard cc-pVXZ and aug-cc-pVXZ (X = D, T, Q, 5, and 6)^{294, 1234, 1220, 55}

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    Partially-augmented “calendar” versions,^{857, 1289} may-, jun-, and jul-cc-pVXZ (X = D, T, Q)

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    Versions with core–valence polarization functions,⁹²⁴ cc-pCVXZ and cc-pwCVXZ (X = D, T, Q)

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    Partially-augmented core–valence polarization basis sets jun-, jul-, and aug-cc-pCVXZ (X = D, T, Q)

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    Pseudopotential (PP) basis sets for heavy elements, cc-pVXZ-PP and aug-cc-pVXZ-PP (X = D, T, Q)^{884, 885, 467}

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  Ahlrichs basis sets⁹⁹³

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  Karlsruhe “def2” basis sets,¹¹⁸⁷ including

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    Augmented versions,⁹⁴⁶ such as def2-SVPD

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    Partially-augmented versions,^Gray:2022 such as def2-ha-SVP and def2-ha-SVP

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  Jensen polarization consistent basis sets^{518, 519, 520}

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  Universal Gaussian basis set (UGBS)²⁵⁶

In addition, Q-Chem supports the following features:

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  Extra diffuse functions available for high quality excited-state calculations.

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  Standard polarization functions.

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  $s$, $p$, $sp$, $d$, $f$, $g$ and $h$ angular momentum types of basis functions (for energy calculations, up to $k$ are supported).

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  Pure and Cartesian basis functions.

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  Mixed basis sets (see Section 8.5).

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  Basis set superposition error (BSSE) corrections.

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  Automatic, on-the-fly generation of a superposition of atomic densities (SAD) guess for any basis set (including general and mixed basis sets) and any SCF level of theory (see Section 4.4.2).

The following $rem keyword controls the basis set: