The dipole moments, dipole polarizabilities, and static hyperpolarizab
ilities of methane and the chloromethanes have been studied at the exp
erimental geometry with the deMon density functional program. Using th
e local density approximation and large basis sets, we computed the di
pole moments of CH4-nCln, n = 0-4, at various finite fields. These fie
ld-dependent dipoles were fitted to polynomials in the fields by least
squares. The extracted static dielectric properties were compared wit
h experimental data and found to be excellent for permanent dipole mom
ents, good for polarizabilities, but only qualitative for hyperpolariz
abilities.