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

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.