On the electric properties of Br2

Abstract

Electric multipole moments and polarizabilities for Br₂ are obtained from finite field self consistent field (SCF), many-body perturbation theory and coupled cluster calculations with large gaussian-type basis sets. At the MP2 level of theory the bond length dependence of the mean and the anisotropy of the dipole polarizability (α_αβ/e ² a ₀ ² E _h ^-1) around the equilibrium bond length of R_e = 2·28105 A is adequately described by

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A very large \[18s15p12d6f] basis set consisting of 330 basis functions yields SCF values α = 44·10 and Δ α = 28·31 e ² a ₀ ² E _h ^-1. Adding electron correlation corrections obtained at the CCSD(T) level of theory and vibrational corrections obtained at the MP2 level, the mean dipole polarizability at the ground vibrational state is estimated at α = 44·74 (to be compared with the experimental value of 45·0) and the anisotropy at Δ α = 25·39 e ² a ₀ ² E _h ^-1. At the MP2 level the mean second dipole hyperpolarizability γ/ e ⁴ a ₀ ⁴ E _h ^-1 varies around R _e as

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SCF, MP2 and CCSD(T) results are combined to give as final theroeticalprediction the estimate of γ = (10·2 ± 1·0) x 10³ e ⁴ a ₀ ⁴ E _h ^-3.