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The definition of frequency‐dependent polarizabilities α(−ω;ω), β(−2ω;ω,ω), β(−ω;ω,0), and β(0;ω,−ω) is discussed, and it is argued that the most convenient definitions are as energy derivatives, a pseudo‐energy being defined as the expectation value of [H−i(∂/∂t)]. This definition outlines a straightforward procedure for obtaining frequency‐dependent polarizabilities for all quantum chemistry methods including those which account for the effects of electron correlation. It is demonstrated at the self‐consistent field level of theory that α^λμ(−ω;ω) cos ωt may be considered as the derivative of the static dipole moment μ^λ with respect to the strength E_ωμ of a frequency‐dependent field E_ωμ cos ωt (as is usual), or as the derivative of an appropriately defined frequency‐dependent dipole moment μ^μ cos ωt with respect to a static field E_0λ. In this way, polarizabilities may be determined from finite static field …