Photoabsorption spectra of small cationic xenon clusters from time-dependent density functional theory

Journal of Chemical Physics 131, 214302 (2009)

Photoabsorption spectra of small cationic xenon clusters from time-dependent density functional theory

M.J.T. Oliveira, F. Nogueira, M.A.L. Marques, A. Rubio

Upon ionization, rare-gas (like Ar and Xe) clusters shift their absorption spectrum from the ultra-violet to the visible. This happens as bonding becomes much stronger due to the removal of an electron from a strongly antibonding orbital. In this Article, we study the absorption spectrum of small cationic xenon clusters (Xe+ , with n = 3, . . . , 35) by means of time-dependent density functional theory. These calculations include relativistic effects through the use of relativistic j-dependent pseudopotentials in a 2-spinor formulation of the Kohn-Sham equations. The peak positions in our calculated spectra are in fairly good agreement with experiment, and confirm that absorption is mainly due to a charged linear core composed of 3, 4, or 5 Xe atoms where the positive charge is localized. However, we found large deviations concerning the oscillator strengths, which can at be least partially explained by an insufficient treatment of relativistic effects in our pseudopotential approach. Furthermore, we found that adequate ground-state geometries are necessary for the correct prediction of the qualitative features of the spectra.

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http://dx.doi.org/10.1063/1.3265767

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