Static hyperpolarisabilities and polarisabilities of Li

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 e 2 a 2 O E h -1 , alpha 2 =1428 e 2 a 0 4 E h -1 , B-5.493*10 4 e 3 a 0 4 E h -2 and gamma =4.3*10 3 e 4 a 0 4 E h -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*10 4 e 4 a 0 4 E h -3 in magnitude.