Eur. Phys. J. D (2013) 67: 43
https://doi.org/10.1140/epjd/e2013-30539-2

Regular Article

Ground state structures, electronic and optical properties of medium-sized Na_n⁺ (n = 9, 15, 21, 26, 31, 36, 41, 50 and 59) clusters from ab initio genetic algorithm^*

¹ Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, P.R. China
² College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, P.R. China

^a e-mail: zhaojj@dlut.edu.cn

Received: 29 August 2012
Received in final form: 4 December 2012
Published online: 7 March 2013

Abstract

Employing genetic algorithm incorporated with density functional theory calculations we determined the lowest-energy structures of cationic Na_n⁺ clusters (n = 9, 15, 21, 26, 31, 36, 41, 50 and 59). We revealed a transition of growth pattern from “polyicosahedral” sequence to the Mackay icosahedral motif at around n = 40. Based on the ground-state structures the size dependent electronic properties of Na_n⁺ clusters including the binding energies, HOMO-LUMO gaps, electron density of states and photoabsorption spectra were discussed. As cluster size increases, the HOMO-LUMO gap of Na_n⁺ cluster gradually reduces and converges to metallic behavior of bulk crystal rapidly. The photoabsorption spectra of Na_n⁺ clusters from our calculations agree with experimental data rather well, confirming the reliability of our theoretical approaches.