Table 1.

Summary of the DFT XC functionals in recent (2020–2021) COVID-19 molecular modeling studies.^a, ^b

Functional	Type	$\mathit{\chi }$c	Exchange functional	Correlation functional	DC class	Description	Selected basis sets in study	Refs
PBE	LDA					Not used in studies reviewed
	GGA	0	PBE	PBE	None	Used to study inactivation mechanism Good at predicting solid-state properties Inaccurate in determining atomization energies and reaction barriers for molecular reactions.	Not mentioned	35., 36., 41.
	Meta-GGA					Not used in studies reviewed
B3LYP	Hybrid GGA	20	B88	Lee-Yang-Parr (LYP)	None	Widely used for many different types of ligand because of its relatively high accuracy and low cost; B3LYP is more suitable for main-group elements than for transition metals	6-31G, 6-31G* 6-311G(d,p) 6-311G* LANL2DZ def2-SVP	14., 15., 18., 20., 25., 32., 33., 37., 42.
B3PW91		20	B88	Perdew-Wang91	None	B3PW91 is similar to B3LYP; performs better for systems with uniform density	6-311++G**	36., 43.
PBE0		25	PBE	PBE	None	PBE0 is PBE functional with a 25% HF exchange functional; used to study inactivation mechanisms through covalent binding	6-31G* 6-311++G**	43., 44
PBE0-D3		25	PBE	PBE	III	PBE0-D3 is PBE0 with semiclassical correction on dispersion; describes thermochemistry better with low numerical complexity; dispersion correction does not affect density expression of system; used to study enzyme–substrate complex dynamical properties	6-31G**	39., 45.
M06-2X	Hybrid meta-GGA	54	M06-2X	M06-2X	II	Performs well in determining main-group thermochemical properties, noncovalent interactions, and barrier heights; however, not suitable for transition metal chemistry	6-311(d,p)	29, 37.
ωB97X-D	RSH GGA	22, 100d	Becke97	Becke97	III	Performs well for bonded interactions and barrier heights	def2-TZVP 6-31+G(d,p)	21., 36., 43.

^aThe types of XC functional are sorted by their levels of accuracy and computational complexity from low (top rows) to high (bottom rows). Some information is from35., 36., 37., 39., 46..

^bAbbreviations: DC Class, Dispersion-Correction Class (defined in³⁹GGA, generalized gradient approximation; GH, global hybrid; RSH, range-separation hybrid.

^c$\chi$: magnitude of the percentage of HF exchange functional in the total exchange functional part.

^d20 for short range exchange functional and 100 for long range exchange functional.