Static hyperpolarisabilities and polarisabilities of Li

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Abstract
The dipole-dipole-quadrupole (B) and second dipole ( gamma ) hyperpolarisabilities, and the dipole ( alpha 1) and quadrupole ( alpha 2) polarisabilities are computed for the ground state of the lithium atom. The results are based on fourth-order Moller-Plesset perturbation theory relative to a coupled unrestricted self-consistent-field wavefunction. The best estimates are alpha 1=164.5 e2a2OEh-1, alpha 2=1428 e2a04Eh-1, B-5.493*104e3a04Eh-2 and gamma =4.3*103e4a04Eh-3. The value of alpha 1 should be accurate to 0.5%, whereas the values of alpha 2 and B should be accurate to 1%. However, the basis set effects on gamma are so large and there is such severe cancellation between the self-consistent-field value and the correlation corrections that even its sign remains uncertain; the true value of gamma is probably less than 1.5*104e4a04Eh-3 in magnitude.