All-Electron Mixed-Basis Calculation to Optimize Structures of Vanadium Micro Clusters

Y. C. Bae*1, H. Osanai*1, K. Ohno*2, M. Sluiter*3, Y. Kawazoe*3

*1CODEC Co. Ltd.,
*2Yokohama National University,
*3Institute for Materials Research, Tohoku University

Introduction
Ab initio molecular dynamics[1][2] based on the local density approximation (LDA)[3] and the adiabatic approximation[4][5] has attracted considerable attention as a conceptually new method, which is capable to describe dynamically the stability and reactivity of any objects including clusters, surfaces and bulk materials at finite temperatures, in principle, without using any parameters. Ohno et al. have developed the all-electron mixed-basis approach which is applicable to the molecular dynamics of objects in any atomic environments[6]. We optimized structures of vanadium microclusters using the approach by Ohno et al.

Method
We calculate vanadium dimer with the local density approximation. We assumed that ther is no spin magnetic moment. The cube is chosen as the unit cell with side length of 0.7nm. The number of plane wave is 925. The cutoff energy for PW's is chosen as 8.7 Ry.

Result
The result of calculation for vanadium dimer is shown in Fig. 1. Here, the abscissa is the bond length and the ordinate is the force and the total energy. In this Figure, the minimum of total energy closes with zero point of the force. It has been already known that V4 is stable on equilateral tetrahedron. Now we are calculating molecules consisting of six and more vanadium atoms.


Fig.1. Force (solid curve) and total energy (broken curve) of vanadium dimer vs bond length.

References

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[4.] M. Born, Z. Physik 40, 167 (1927).
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[6.] K. Ohno, Y. Maruyama, H. Kamiyama, E. Bei, K. Shiga, Z.-Q. Li, K. Esfarjani, and Y. Kawazoe, in Mesoscopic Dynamics of Fracture: Computational Materials Design, Vol. 1, edited by H. Kitagawa, T. Aihara, Jr., and Y. Kawazoe, Advances in Materials Research Series (Springer, Berlin, Heidelberg, 1998) pp. 210.