A method of computational chemistry in which the electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule. The molecule has a set of molecular orbitals (see orbital). The usual technique is to obtain molecular orbitals by a linear combination of atomic orbitals (LCAO). The use of correlation diagrams is very helpful in molecular-orbital theory. See also density-functional theory; valence-bond theory.