Structures and electronic properties of $\hbox {W}_{m}\hbox {Cu}_{n}\,(n + m \le 7)$ clusters

Abstract

Geometric and electronic structures of $\hbox {W}_{m}\hbox {Cu}_{n}\, (m + n \le 7)$ cluster have been systematically calculated by density functional theory at the generalized gradient approximation level for ground-state structures. $\hbox {W}_{m}\hbox {Cu}_{n}$ clusters with $n = 1, 3, 5$ tend to form bipyramid structures, whereas $\hbox {WCu}_{n}$ favour planar shapes except for $\hbox {WCu}_{5}$. The configurations of $\hbox {W}_{m}\hbox {Cu}_{n}$ clusters are more sensitive to the Cu atoms than the W atoms, while the average atomic binding energies and the total magnetic moments are determined by W atoms. The calculated second-order differences in energies and HOMO–LOMO energy gaps show pronounced odd–even oscillating behaviours. From the Mulliken electron population analysis, we found that Cu 4p and W 6p orbitals exhibit electronic charges and both Cu 4s and W 6s orbitals transfer electronic charges to the W 5d orbital, which lead to the extension of W–Cu bond lengths.