Journal Article Research Support, Non-U.S. Gov't density functional theory potential acting on an electron in a molecule Alcohols ELF Fermi hole IQA QM/MM QTAIM X-ray diffraction chemical bond cyclo[18]carbon delocalization index delocalization of electrons descriptors of chemical bonding electron density electrostatic potential exchange correlation halogen bond hydrogen bond non-covalent interactions one-electron density matrix one-electron potential one-electron potentials quantum chemistry quantum crystallography reduced density gradient source function