Gauge origin independence

S.P.A. Sauer, 1. Paidarov J. Oddershede, Correlated and Gauge Origin Independent Calculations of Magnetic Properties. 1. Triply Bonded Molecules, Mol. Phys. 81 (1994) 87. 

Field-dependent basis orbitals as vj (r, G, B) — Uj (f) exp(- (BxG)-f) should be used, resulting in a similar transformation of the electron field operators. Such field-dependent orbitals would guarantee gauge origin independence even in a finite basis. In this expression, G is the position of orbital Uj with respect to an arbitrary origin and the electron coordinate r is given in the same coordinate system. Usually the atomic orbitals are centered at the nuclear positions. In such cases, Rg takes the place of G for the orbital Vj f, Rg, By. 

Bak KL, J0rgensen P, Helgaker T, Ruud K, Jensen HJAa (1993) Gauge-origin independent multiconfigurational self-consistent-field theory for vibrational circular dichroism. J Chem Phys 98 8873-8887... 

T. Baba, H. Fukui. Calculation of nuclear magnetic shieldings Xin. Gauge-origin independent relativistic effects. J. Chem. Phys., 110 (1999) 131-137. 

Ideally, for magnetic properties, gauge-origin independent atomic orbitals (GIAO) > should be used as discussed earlier. These orbitals reduce the sensitivity of calculated properties to the size of the basis set and therefore permit applications to larger molecules. The use of GIAO for VCD calculations has recently been reported. ... 

Due to the use of the velocity form of the operators, the TPCD given by this expression is gauge-origin independent. The parameters b, Z>2 and b are numbers. 

Sauer, S. P. A., Paidarova, I., and Oddershede, J. (1994a). Correlated and gauge origin independent calculations of magnetic properties. I. Triply bonded molecules. Mol. Phys., 81, 87-118. 

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