8.10.4 A Brief Guide toQ-Chem’s Built-In ECPs‣ 8.10 Effective Core Potentials (ECPs) ‣ Chapter 8 Basis Sets and Effective Core Potentials ‣ Q-Chem 6.2 User’s Manual

8.10.4.1 Introduction

The remainder of this Chapter consists of a brief reference guide to Q-Chem’s built-in ECPs. The ECPs vary in their complexity and their accuracy and the purpose of the guide is to enable the user quickly and easily to decide which ECP to use in a planned calculation.

The following information is provided for each ECP:

•

The elements for which the ECP is available in Q-Chem. This is shown on a schematic Periodic Table by shading all the elements that are not supported.
•

The literature reference for each element for which the ECP is available in Q-Chem.
•

The matching orbital basis set that Q-Chem will use for light (i.e.. non-ECP atoms). For example, if the user requests SRSC ECPs—which are defined only for atoms beyond argon—Q-Chem will use the 6-311G basis set for all atoms up to Ar.
•

The core electrons that are replaced by the ECP. For example, in the fit-LANL2DZ ECP for the Fe atom, the core is [Ne], indicating that the $1s$ , $2s$ and $2p$ electrons are removed.
•

The maximum spherical harmonic projection operator that is used for each element. This often, but not always, corresponds to the maximum orbital angular momentum of the core electrons that have been replaced by the ECP. For example, in the fit-LANL2DZ ECP for the Fe atom, the maximum projector is of $P$ -type.
•

The number of valence basis functions of each angular momentum type that are present in the matching orbital basis set. For example, in the matching basis for the fit-LANL2DZ ECP for the Fe atom, there the three $s$ shells, three $p$ shells and two $d$ shells. This basis is therefore almost of triple-split valence quality.

8.10.4.2 The fit-HWMB ECP

fit-HWMB is not available for shaded elements

(a)	No ECP; Pople STO-3G basis used
(b)	Wadt & Hay (Ref. 1324 Wadt W. R., Hay P. J. J. Chem. Phys. (1985), 82, pp. 284. Link )
(c)	Hay & Wadt (Ref. 496 Hay P. J., Wadt W. R. J. Chem. Phys. (1985), 82, pp. 299. Link )
(d)	Hay & Wadt (Ref. 495 Hay P. J., Wadt W. R. J. Chem. Phys. (1985), 82, pp. 270. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(1s)
Li–Ne	none	none	(2s,1p)
Na–Ar	[Ne]	$P$	(1s,1p)
K–Ca	[Ne]	$P$	(2s,1p)
Sc–Cu	[Ne]	$P$	(2s,1p,1d)
Zn	[Ar]	$D$	(1s,1p,1d)
Ga–Kr	[Ar]+3d	$D$	(1s,1p)
Rb–Sr	[Ar]+3d	$D$	(2s,1p)
Y–Ag	[Ar]+3d	$D$	(2s,1p,1d)
Cd	[Kr]	$D$	(1s,1p,1d)
In–Xe	[Kr]+4d	$D$	(1s,1p)
Cs–Ba	[Kr]+4d	$D$	(2s,1p)
La	[Kr]+4d	$D$	(2s,1p,1d)
Hf–Au	[Kr]+4d+4f	$F$	(2s,1p,1d)
Hg	[Xe]+4f	$F$	(1s,1p,1d)
Tl–Bi	[Xe]+4f+5d	$F$	(1s,1p)

Table 8.10: Supported elements for the fit-HWMB ECP.

8.10.4.3 The fit-LANL2DZ ECP

fit-LANL2DZ is not available for shaded elements

(a)	No ECP; Pople 6-31G basis used
(b)	Wadt & Hay (Ref. 1324 Wadt W. R., Hay P. J. J. Chem. Phys. (1985), 82, pp. 284. Link )
(c)	Hay & Wadt (Ref. 496 Hay P. J., Wadt W. R. J. Chem. Phys. (1985), 82, pp. 299. Link )
(d)	Hay & Wadt (Ref. 495 Hay P. J., Wadt W. R. J. Chem. Phys. (1985), 82, pp. 270. Link )
(e)	Hay (Ref. 497 Hay P. J. J. Chem. Phys. (1983), 79, pp. 5469. Link )
(f)	Hay & Martin (Ref. 494 Hay P. J., Martin R. L. J. Chem. Phys. (1998), 109, pp. 3875. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(2s)
Li–Ne	none	none	(3s,2p)
Na–Ar	[Ne]	$P$	(2s,2p)
K–Ca	[Ne]	$P$	(3s,3p)
Sc–Cu	[Ne]	$P$	(3s,3p,2d)
Zn	[Ar]	$D$	(2s,2p,2d)
Ga–Kr	[Ar]+3d	$D$	(2s,2p)
Rb–Sr	[Ar]+3d	$D$	(3s,3p)
Y–Ag	[Ar]+3d	$D$	(3s,3p,2d)
Cd	[Kr]	$D$	(2s,2p,2d)
In–Xe	[Kr]+4d	$D$	(2s,2p)
Cs–Ba	[Kr]+4d	$D$	(3s,3p)
La	[Kr]+4d	$D$	(3s,3p,2d)
Hf–Au	[Kr]+4d+4f	$F$	(3s,3p,2d)
Hg	[Xe]+4f	$F$	(2s,2p,2d)
Tl	[Xe]+4f+5d	$F$	(2s,2p,2d)
Pb–Bi	[Xe]+4f+5d	$F$	(2s,2p)
U–Pu	[Xe]+4f+5d	$F$	(3s,3p,2d,2f)

Table 8.11: Supported elements for the fit-LANL2DZ ECP.

Note that Q-Chem 4.2.2 and later versions also support the LANL2DZ-SV basis, which employs SV basis functions (instead of 6-31G) on H, Li-Ne elements (like some other quantum chemistry packages).

8.10.4.4 The fit-SBKJC ECP

fit-SBKJC is not available for shaded elements

(a)	No ECP; Pople 3-21G basis used
(b)	Stevens, Basch, & M. Krauss (Ref. 1223 Stevens W. J., Basch H., Krauss M. J. Chem. Phys. (1984), 81, pp. 6026. Link )
(c)	Stevens, Krauss, Basch, & Jasien (Ref. 1224 Stevens W. J. et al. Can. J. Chem. (1992), 70, pp. 612. Link )
(d)	Cundari & Stevens (Ref. 274 Cundari T. R., Stevens W. J. J. Chem. Phys. (1993), 98, pp. 5555. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(2s)
Li–Ne	[He]	$S$	(2s,2p)
Na–Ar	[Ne]	$P$	(2s,2p)
K–Ca	[Ar]	$P$	(2s,2p)
Sc–Ga	[Ne]	$P$	(4s,4p,3d)
Ge–Kr	[Ar]+3d	$D$	(2s,2p)
Rb–Sr	[Kr]	$D$	(2s,2p)
Y–In	[Ar]+3d	$D$	(4s,4p,3d)
Sn–Xe	[Kr]+4d	$D$	(2s,2p)
Cs–Ba	[Xe]	$D$	(2s,2p)
La	[Kr]+4d	$F$	(4s,4p,3d)
Ce–Lu	[Kr]+4d	$D$	(4s,4p,1d,1f)
Hf–Tl	[Kr]+4d+4f	$F$	(4s,4p,3d)
Pb–Rn	[Xe]+4f+5d	$F$	(2s,2p)

Table 8.12: Supported elements for the fit-SBKJC ECP.

8.10.4.5 The fit-CRENBS ECP

fit-CRENBS is not available for shaded elements

(a)	No ECP; Pople STO-3G basis used
(b)	Hurley, Pacios, Christiansen, Ross, & Ermler (Ref. 570 Hurley M. M., Pacios L. F., Christiansen P. A. J. Chem. Phys. (1986), 84, pp. 6840. Link )
(c)	LaJohn, Christiansen, Ross, Atashroo & Ermler (Ref. 706 LaJohn L. A. et al. J. Chem. Phys. (1987), 87, pp. 2812. Link )
(d)	Ross, Powers, Atashroo, Ermler, LaJohn & Christiansen (Ref. 1107 Ross R. B. et al. J. Chem. Phys. (1990), 93, pp. 6654. Link )
(e)	Nash, Bursten, & Ermler (Ref. 920 Nash C. S., Bursten B. E., Ermler W. C. J. Chem. Phys. (1997), 106, pp. 5133. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(1s)
Li–Ne	none	none	(2s,1p)
Na–Ar	none	none	(3s,2p)
K–Ca	none	none	(4s,3p)
Sc–Zn	[Ar]	$P$	(1s,0p,1d)
Ga–Kr	[Ar]+3d	$D$	(1s,1p)
Y–Cd	[Kr]	$D$	(1s,1p,1d)
In–Xe	[Kr]+4d	$D$	(1s,1p)
La	[Xe]	$D$	(1s,1p,1d)
Hf–Hg	[Xe]+4f	$F$	(1s,1p,1d)
Tl–Rn	[Xe]+4f+5d	$F$	(1s,1p)

Table 8.13: Supported elements for the fit-CRENBS ECP.

8.10.4.6 The fit-CRENBL ECP

(a)	No ECP; Pople 6-311G basis used
(b)	Pacios & Christiansen (Ref. 963 Pacios L. F., Christiansen P. A. J. Chem. Phys. (1985), 82, pp. 2664. Link )
(c)	Hurley, Pacios, Christiansen, Ross, & Ermler (Ref. 570 Hurley M. M., Pacios L. F., Christiansen P. A. J. Chem. Phys. (1986), 84, pp. 6840. Link )
(d)	LaJohn, Christiansen, Ross, Atashroo, & Ermler (Ref. 706 LaJohn L. A. et al. J. Chem. Phys. (1987), 87, pp. 2812. Link )
(e)	Ross, Powers, Atashroo, Ermler, LaJohn, & Christiansen (Ref. 1107 Ross R. B. et al. J. Chem. Phys. (1990), 93, pp. 6654. Link )
(f)	Ermler, Ross, & Christiansen (Ref. 348 Ermler W. C., Ross R. B., Christiansen P. A. Int. J. Quantum Chem. (1991), 40, pp. 829. Link )
(g)	Ross, Gayen, & Ermler (Ref. 1106 Ross R. B., Gayen S., Ermler W. C. J. Chem. Phys. (1994), 100, pp. 8145. Link )
(h)	Nash, Bursten, & Ermler (Ref. 920 Nash C. S., Bursten B. E., Ermler W. C. J. Chem. Phys. (1997), 106, pp. 5133. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(3s)
Li–Ne	[He]	S	(4s,4p)
Na–Mg	[He]	S	(6s,4p)
Al–Ar	[Ne]	P	(4s,4p)
K–Ca	[Ne]	P	(5s,4p)
Sc–Zn	[Ne]	P	(7s,6p,6d)
Ga–Kr	[Ar]	P	(3s,3p,4d)
Rb–Sr	[Ar]+3d	D	(5s,5p)
Y–Cd	[Ar]+3d	D	(5s,5p,4d)
In–Xe	[Kr]	D	(3s,3p,4d)
Cs–La	[Kr]+4d	D	(5s,5p,4d)
Ce–Lu	[Xe]	D	(6s,6p,6d,6f)
Hf–Hg	[Kr]+4d+4f	F	(5s,5p,4d)
Tl–Rn	[Xe]+4f	F	(3s,3p,4d)
Fr–Ra	[Xe]+4f+5d	F	(5s,5p,4d)
Ac–Pu	[Xe]+4f+5d	F	(5s,5p,4d,4f)
Am–Lr	[Xe]+4f+5d	F	(0s,2p,6d,5f)

Table 8.14: Supported elements for the fit-CRENBL ECP.

8.10.4.7 The SRLC ECP

SRLC is not available for shaded elements

(a)	No ECP; Pople 6-31G basis used
(b)	Fuentealba, Preuss, Stoll, & von Szentpály (Ref. 383 Fuentealba P. et al. Chem. Phys. Lett. (1982), 89, pp. 418. Link )
(c)	Fuentealba, von Szentpály, Preuss, & Stoll (Ref. 385 Fuentealba P. et al. J. Phys. B: At. Mol. Opt. Phys. (1985), 18, pp. 1287. Link )
(d)	Bergner, Dolg, Küchle, Stoll, & Preuss (Ref. 106 Bergner A. et al. Mol. Phys. (1993), 80, pp. 1431. Link )
(e)	Nicklass, Dolg, Stoll, & Preuss, (Ref. 927 Nicklass A. et al. J. Chem. Phys. (1995), 102, pp. 8942. Link )
(f)	Schautz, Flad, & Dolg (Ref. 1125 Schautz F., Flad H.-J., Dolg M. Theor. Chem. Acc. (1998), 99, pp. 231. Link )
(g)	Fuentealba, Stoll, von Szentpály, Schwerdtfeger, & Preuss (Ref. 384 Fuentealba P. et al. J. Phys. B: At. Mol. Opt. Phys. (1983), 16, pp. L323. Link )
(h)	von Szentpály, Fuentealba, Preuss, & Stoll (Ref. 1313 von Szentpály L. et al. Chem. Phys. Lett. (1982), 93, pp. 555. Link )
(i)	Küchle, Dolg, Stoll, & Preuss (Ref. 694 Küchle W. et al. Mol. Phys. (1991), 74, pp. 1245. Link )
(j)	Küchle (Ref. )

Element	Core	Max Projector	Valence
H–He	none	none	(2s)
Li–Be	[He]	$P$	(2s,2p)
B–N	[He]	$D$	(2s,2p)
O–F	[He]	$D$	(2s,3p)
Ne	[He]	$D$	(4s,4p,3d,1f)
Na–P	[Ne]	$D$	(2s,2p)
S–Cl	[Ne]	$D$	(2s,3p)
Ar	[Ne]	$F$	(4s,4p,3d,1f)
K–Ca	[Ar]	$D$	(2s,2p)
Zn	[Ar]+3d	$D$	(3s,2p)
Ga–As	[Ar]+3d	$F$	(2s,2p)
Se–Br	[Ar]+3d	$F$	(2s,3p)
Kr	[Ar]+3d	$G$	(4s,4p,3d,1f)
Rb–Sr	[Kr]	$D$	(2s,2p)
In–Sb	[Kr]+4d	$F$	(2s,2p)
Te–I	[Kr]+4d	$F$	(2s,3p)
Xe	[Kr]+4d	$G$	(4s,4p,3d,1f)
Cs–Ba	[Xe]	$D$	(2s,2p)
Hg–Bi	[Xe]+4f+5d	$G$	(2s,2p,1d)
Po–At	[Xe]+4f+5d	$G$	(2s,3p,1d)
Rn	[Xe]+4f+5d	$G$	(2s,2p,1d)
Ac–Lr	[Xe]+4f+5d	$G$	(5s,5p,4d,3f,2g)

Table 8.15: Supported elements for the SRLC ECP.

8.10.4.8 The SRSC ECP

SRSC is not available for shaded elements

(a)	No ECP; Pople 6-311G basis used
(b)	Leininger, Nicklass, Küchle, Stoll, Dolg, & Bergner (Ref. 755 Leininger T. et al. Chem. Phys. Lett. (1996), 255, pp. 274. Link )
(c)	Kaupp, Schleyer, Stoll, & Preuss (Ref. 636 Kaupp M. et al. J. Chem. Phys. (1991), 94, pp. 1360. Link )
(d)	Dolg, Wedig, Stoll, & Preuss (Ref. 327 Dolg M. et al. J. Chem. Phys. (1987), 86, pp. 866. Link )
(e)	Andrae, Häußermann, Dolg, Stoll, & Preuss (Ref. 45 Andrae D. et al. Theor. Chem. Acc. (1990), 77, pp. 123. Link )
(f)	Dolg, Stoll, & Preuss (Ref. 325 Dolg M., Preuss H. J. Chem. Phys. (1989), 90, pp. 1730. Link )
(g)	Küchle, Dolg, Stoll, & Preuss (Ref. 695 Küchle W. et al. J. Chem. Phys. (1994), 100, pp. 7535. Link )
(h)	Dolg, Stoll, Preuss, & Pitzer (Ref. 326 Dolg M. et al. J. Phys. Chem. (1993), 97, pp. 5852. Link )

Element	Core	Max Projector	Valence
H–He	none	none	(3s)
Li–Ne	none	none	(4s,3p,1d)
Na–Ar	none	none	(6s,5p,1d)
K	[Ne]	$F$	(5s,4p)
Ca	[Ne]	$F$	(4s,4p,2d)
Sc–Zn	[Ne]	$D$	(6s,5p,3d)
Rb	[Ar]+3d	$F$	(5s,4p)
Sr	[Ar]+3d	$F$	(4s,4p,2d)
Y–Cd	[Ar]+3d	$F$	(6s,5p,3d)
Cs	[Kr]+4d	$F$	(5s,4p)
Ba	[Kr]+4d	$F$	(3s,3p,2d,1f)
Ce–Yb	[Ar]+3d	$G$	(5s,5p,4d,3f)
Hf–Pt	[Kr]+4d+4f	$G$	(6s,5p,3d)
Au	[Kr]+4d+4f	$F$	(7s,3p,4d)
Hg	[Kr]+4d+4f	$G$	(6s,6p,4d)
Ac–Lr	[Kr]+4d+4f	$G$	(8s,7p,6d,4f)

Table 8.16: Supported elements for the SRSC ECP.

8.10.4.9 The Karlsruhe “def2” ECPs

For elements Rb–Rn, all the Karlsruhe “def2” basis sets are paired with a common set of ECPs. ¹³³⁶ Weigend F., Ahlrichs R.
Phys. Chem. Chem. Phys.
(2005), 7, pp. 3297. Link It is briefly summarized in the table below (the number of valence basis functions depend on the basis set in use, so it is not presented):

Element	Core	Max Projector
H–Kr	none	none
Rb–Xe	[Ar]+3d	$D$
Cs–La	[Kr]+4d	$D$
Hf–Rn	[Kr]+4d+4f	$D$

Table 8.17: Supported elements for the def2 ECP.

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8.10.4 A Brief Guide to Q-Chem’s Built-In ECPs