XC
XC = Combination of functionals
| Default: XC | = GGA | if the GGA tag is used |
| = METAGGA | if the METAGGA tag is used | |
| = The functional specified by LEXCH in the POTCAR file | if neither GGA nor METAGGA is used |
Description: XC specifies a combination of exchange-correlation functionals.
A combination of semilocal (LDA, GGA, and METAGGA) functionals can be set with the XC tag, which provides much more flexibility in the choice of the functional compared to the GGA and METAGGA tags. The functionals that can be combined are the functionals implemented in VASP (listed at GGA and METAGGA) and the functionals implemented in Libxc[1][2][3] (listed on the Libxc website[4]). The combination can consist of up to 100 components; for each, a multiplication factor can be set with the XC_C tag.
Examples of INCAR
XC = PE PS XC_C = 0.5 0.5
XC = SCAN_X PBE_C
- 70% of B88[8] (from Libxc) and 30% of PBE[5] for exchange and 100% of LYP (from Libxc) for correlation[9]
XC = GGA_X_B88 PBE_X GGA_C_LYP XC_C = 0.7 0.3 1.0
- 15% of HF, 63.75% of PBE[5], and 21.25% of B88[8] (from Libxc) for exchange and 75% of PBE[5] and 25% of LYP[9] (from Libxc) for correlation
LHFCALC = .TRUE. XC = PE GGA_X_B88 GGA_C_LYP XC_C = 0.75 0.25 0.25 AEXX = 0.15 AGGAX = 0.85
- In this example, the PBE exchange is multiplied by and the B88 exchange by .
Related tags and articles
XC_C, GGA, METAGGA LIBXC1, LIBXC2, ALDAX, ALDAC, AGGAX, AGGAC, AMGGAX, AMGGAC
References
- ↑ M. A. L. Marques, M. J. T. Oliveira, and T. Burnus, Comput. Phys. Commun., 183, 2272 (2012).
- ↑ S. Lehtola, C. Steigemann, M. J. T. Oliveira, and M. A. L. Marques, SoftwareX, 7, 1 (2018).
- ↑ https://libxc.gitlab.io
- ↑ https://libxc.gitlab.io/functionals/
- ↑ a b c d e J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett., 77, 3865 (1996).
- ↑ J. P. Perdew, A. Ruzsinszky, G. I. Csonka, O. A. Vydrov, G. E. Scuseria, L. A. Constantin, X. Zhou, and K. Burke, Phys. Rev. Lett. 100, 136406 (2008).
- ↑ J. Sun, A. Ruzsinszky, and J. P. Perdew, Phys. Rev. Lett. 115, 036402 (2015).
- ↑ a b A. D. Becke, Density-functional exchange-energy approximation with correct asymptotic behavior, Phys. Rev. A 38, 3098 (1988).
- ↑ a b C. Lee, W. Yang, and R. G. Parr, Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density, Phys. Rev. B 37, 785 (1988).