Magnetizability and carbon-13-shielding surfaces for the methane molecule

Magnetizability (chi) and carbon-13 shielding (sigma) surfaces have been calculated for the methane molecule using a Hartree-Fock wave-function. Correlation corrections to the diamagnetic parts of the surfaces have been calculated using a CAS SCF wavefunction. The results show that the properties are very sensitive to bond stretching with chi| increasing and sigma decreasing with increasing bond length. They are less sensitive to change of interbond angle. The surfaces are given in terms of the coefficients of Taylor series expansions about equilibrium geometry with respect to both symmetry coordinates and valence coordinates.