Electronic structure and magnetism of small V and Cr clusters.

Abstract

The electronic structure and magnetism of ${\mathrm{V}}_{9}$, ${\mathrm{V}}_{15}$, ${\mathrm{Cr}}_{9}$, and ${\mathrm{Cr}}_{15}$ clusters having body centered cubic (bcc) geometry have been studied using a Gaussian orbital basis and the local spin density approximation. For ${\mathrm{V}}_{9}$ and ${\mathrm{Cr}}_{9}$, calculations were made for several different lattice spacings. Our calculated moment of 0.33${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ of ${\mathrm{V}}_{9}$ is much smaller than the previously calculated 2.89${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ and is in very good agreement with a recent experiment. Our calculated moments of 0.67${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, 0.07${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, and 0.40${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, respectively for ${\mathrm{Cr}}_{9}$, ${\mathrm{V}}_{15}$, and ${\mathrm{Cr}}_{15}$ at the 0 K bulk lattice spacing are also in good agreement with experiment. But ${\mathrm{Cr}}_{9}$ was found to have a transition near the bulk lattice spacing such that the moment becomes very large above the room temperature lattice spacing. Calculations of ${\mathrm{V}}_{9}$ and ${\mathrm{Cr}}_{9}$ at various interatomic distances show that they go through small magnetic moment to large moment transitions at certain distances, similar to the nonmagnetic to magnetic transition in bulk phase. The density of states profiles of ${\mathrm{V}}_{15}$ and ${\mathrm{Cr}}_{15}$ show the features characteristic of the bulk as had been the case in our previous calculations of Fe, Ni, and Cu.