Formulated by Becke and Edgecombe,46 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 structure.270 The function has values that lie between 0 and 1, with representing perfect localization and 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, only the -spin ELF is calculated whereas for open-shell systems (spin-unrestricted calculations), both - and -spin ELFs are computed.492
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, which uses the newer $plots format.