How large is the static electric (hyper)polarizability anisotropy in HXeI?

An extensive conventional ab initio and density functional theory investigation reveals that HXeI is a polar molecule with large multipole moments and highly anisotropic (hyper)polarizability. At the CCSD(T) level of theory our best values for the mean (hyper)polarizability are (alpha) over bar /e(2)a(0)(2)E(h)(-1)=101.46, (beta) over bar /e(3)a(0)(3)E(h)(-2)=-850.7, and (gamma) over bar /e(4)a(0)(4)E(h)(-3)=18.7x10(3). The corresponding anisotropies are Delta alpha/e(2)a(0)(2)E(h)(-1)=119.66, Delta beta/e(3)a(0)(3)E(h)(-2)=-2518.7, Delta(1)gamma/e(4)a(0)(4)E(h)(-3)=-249.1x10(3), and Delta(2)gamma/e(4)a(0)(4)E(h)(-3)=-99.6x10(3). The longitudinal components of the (hyper)polarizability are dominant. Our value for the anisotropy of the dipole polarizability is considerably larger than the recent empirical estimate of 22.9 e(2)a(0)(2)E(h)(-1) [N. H. Nahler , J. Chem. Phys. 119, 224 (2003)]. The results of the insertion of Xe into HI are quantified by the calculation of the differential (hyper)polarizability at the MP2 level of theory: (alpha) over bar (diff)equivalent to(alpha) over bar (HXeI)-alpha(HI)-(alpha) over bar (Xe)=36.29 e(2)a(0)2E(h)-1 and (gamma) over bar (diff)equivalent to(gamma) over bar (HXeI)-(gamma) over bar (HI)-(gamma) over bar (Xe)=18.1x10(3) e(4)a(0)(4)E(h)(-3). (C) 2008 American Institute of Physics.