Polarizabilities of confined two-electron systems: the 2-electron quantum dot, the hydrogen anion, the helium atom and the lithium cation

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The static dipole polarizabilities of two-electron systems confined by a spherical harmonic-oscillator potential ω have been calculated by the coupled-cluster CCSD method. The combined effect of the confining potential ω and the central electrostatic field on the polarizabilities of the quantum dot, and the confined systems, H−, He and Li+, respectively, have been investigated. The polarizabilities of the quantum dot can be calculated analytically. The polarizability α of the 2-electron quantum dot for ω = 0.01 is calculated to be 19 996 au, in perfect agreement with the exact value, 20 000 au. Already medium confinement, ω = 1.0, reduces α to 2.00 au. The decrease of the polarizability is smaller for H− (α = 216.1 au for ω = 0.0 and 0.985 au for ω = 1.0), and much smaller for He and Li+ (1.3819 and 0.3813 au for He for ω = 0.0 and ω = 1.0, respectively, and 0.1921 and 0.128 au for Li+). The theoretical polarizabilities for unconfined (ω = 0.0) H−, He and the Li+ cation are in very good agreement with the best published theoretical and/or experimental data. Our final polarizability for H−, 216.0±0.5 au, appears to be one of the most accurate values published so far. The optimization procedures of basis sets applicable to calculations of polarizabilities of systems confined by a spherical harmonic-oscillator potential are presented.