Dipole, dipole-quadrupole, and dipole-octopole polarizability of adamantane, C10H16, from refractive index measurements, depolarized collision-induced light scattering, conventional ab initio and density functional theory calculations

Refractive index (RI) measurements, depolarized collision-induced light (CI LS) scattering and ab initio quantum chemical calculations are used to dete rmine the dipole (alpha), dipole-quadrupole (A), and dipole-octopole polari zability (E) of adamantane, C10H16. For this molecule of symmetry group T-d the three polarizabilities can be represented by a single scalar quantity. From experiment we obtain for the static dipole polarizability at T approx imate to 400-500 K 107.5 +/-1.1 e(2)a(0)(2)E(h)(-1), and for the higher pol arizabilities \A \ =102.0 +/-7.8 e(2)a(0)(3)E(h)(-1), and \E oe =720 +/- 80 e(2)a(0)(4)E(h)(-1). We have performed conventional ab initio and density functional theory calculations with specifically designed basis sets. A ver y large [4s3p3d1f/3s2p1d] basis set consisting of 574 basis functions is th ought to provide near-Hartree-Fock values for alpha ,A and E: alpha =101.72 e(2)a(0)(2)E(h)(-1), A=-6.5 e(2)a(0)(3)E(h)(-1), and E=-71.0 e(2)a(0)(4)E( h)(-1). Our final theoretical estimates for these properties are alpha =107 .5 +/-1.0 e(2)a(0)(2)E(h)(-1), A=-8.0 +/-1.5 e(2)a(0)(3)E(h)(-1), and E=-76 .5 +/-5.5 e(2)a(0)(4)E(h)(-1). Very strong electron correlation effects are found for both the first (beta) and second (gamma) hyperpolarizability. Ou r estimate for beta equivalent to beta (xyz) and the mean <(<gamma>)over ba r> are 41.4 +/-5.6 e(3)a(0)(3)E(h)(-2) and (25 +/-2)x10(3) e(4)a(0)(4)E(h)( -3), respectively. For the octopole and hexadecapole moments we propose Ome ga=-4.4 +/-0.2 ea(0)(3) and Phi=-100.8 +/-5.5 ea(0)(4). The basis sets cons tructed in this work should provide reliable computational tools for the st udy of intermolecular interactions of adamantane. (C) 2001 American Institu te of Physics.