London gauge theory

London orbitals were introduced by Fritz London, who in 1937 used Hiickel theory to calculate the contribution to the magnetizability from the ring currents in the 7r-orbital backbone of some aromatic molecules [13]. The great virtue of London s approach is that each individual AO—the building blocks of molecular wave functions—has been harnessed to respond correctly (to first order at least) to the application of an external magnetic field, irrespective of the choice of the external gauge origin. Moreover, since, in London s approach, only the atomic orbitals are modified, this method is fully transparent to the treatment of the electronic structure otherwise. 

The method of choice for calculating optical rotations includes electronic ground state ab initio time-dependent density functional theory (TDDFT) the use of London orbitals, also referred to as gauge-invariant (including)... 

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