Formulated by Becke and Edgecombe74, the electron localization function (ELF),
is a measure of electron localization. It is derived from the Hartree-Fock conditional pair probability and can reveal information about bonding and shell structure279. ELF values lie between 0 and 1, with an ELF=1 representing perfect localization,and an ELF=1/2 representing electron-gas like pair probability. To generate ELF plots with Q-Chem, set the PLOT_ELF $rem variable to TRUE. For closed-shell systems, the spin ELF is calculated. For open-shell systems, the , and spin-adapted ELFs are calculated485.
The following example illustrates the calculation of the ELF for a water molecule.
$molecule 0 1 O -4.5320698567 0.2524215916 0.0130780103 H -3.5641829319 0.2173288989 -0.0173259969 H -4.8109190521 -0.4489616171 -0.5945943692 $end $rem jobtype opt method b3lyp basis 6-31g* plot_elf true make_cube_files true $end $plots water 50 -7 7 50 -4 4 50 -4 4 0 1 0 0 0 $end
(Please refer also to elf_methane.in the $QC/samples directory. This uses the newer $plots format).