Ab initio finite field (hyper)polarizability computations on stoichiometric gallium arsenide clusters GanAsn (n=2-9)
Résumé
We report reliable ab initio finite field (hyper)polarizability values at Hartree-Fock and second order Møller-Plesset perturbation theory (MP2) levels of theory for different geometrical configurations of small gallium arsenide clusters Gan Asn with n=2-5. We relied on all-electron basis sets and pseudopotentials suitable for (hyper)polarizability calculations. In each case, we used structures that have been established in the literature after we optimized their geometries at B3LYP/cc-pVTZ-PP level of theory. Our results suggest that the first order hyperpolarizability (Β) is much more sensitive to the special geometric features than the second order hyperpolarizability (γ). For the most stable configurations up to ten atoms the second order hyperpolarizability at MP2 level of theory varies between 15× 104 and 32× 104 e4 a04 Eh -3. In addition, we examined the polarizability per atom evolution versus the cluster size for Gan Asn with n=2-9. Our work extends earlier theoretical studies which were limited to eight atoms and exposes that the polarizability/atom of the most stable stoichiometric configurations up to Ga9 As9 continues the monotonic downward trend with increasing size. Lastly, from the methodological point of view, our analysis shows that apart from polarizabilities, augmented pseudopotentials yield reliable first and second hyperpolarizability values as well. © 2007 American Institute of Physics.