Static (Hyper)Polarizability of CH3X, X=F, Cl, Br and I

We present a systematic study of static dipole polarizability (α_αβ) and static first (β_αβγ) and second (γ_αβγδ) hyperpolarizability of the monohalogenated methanes, CH₃X, X=F, Cl, Br, I. All properties have been obtained from finite-field Møller-Plesset Perturbation theory and Coupled Cluster calculations with flexible, especially designed gaussian-type basis sets. Good agreement is observed between experimental and theoretical values of the dipole polarizability. In the other hand the comparison in the case of the hyperpolarizabilities is not obvious.