Structural stability and magnetic properties of \(\hbox {Cu}_{m}\hbox {Co}_{n}\hbox {NO}\) (\(m+n = 2\)–7) clusters

A theoretical study of NO adsorption on \(\hbox {Cu}_{m}\hbox {Co}_{n}\) (2 \(\le m+n \le \) 7) clusters was carried out using a density functional method. Generally, NO is absorbed at the top site via the N atom, except in \(\hbox {Cu}_{3}\hbox {NO}\) and \(\hbox {Cu}_{5}\hbox {NO}\) clusters, where NO is located at the bridge site. \(\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{2}\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Co}_{5}\hbox {NO}\), \(\hbox {Cu}_{2}\hbox {Co}_{4}\hbox {NO}\) and \(\hbox {Cu}_{6}\hbox {CoNO}\) clusters have larger adsorption energies, indicating that NO of these clusters are more easily adsorbed. After adsorption, N–O bond is weakened and the activity is enhanced as a result of vibration frequency of N–O bond getting lower than that of a single NO molecule. \(\hbox {Cu}_{2}\hbox {CoNO}\), \(\hbox {Cu}_{3}\hbox {CoNO}\), \(\hbox {Cu}_{2}\hbox {Co}_{2}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {Co}_{3}\hbox {NO}\) and \(\hbox {Cu}\hbox {Co}_{5}\hbox {NO}\) clusters are more stable than their neighbours, while CuCoNO, \(\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {CoNO}\), \(\hbox {Cu}_{2}\hbox {Co}_{3}\hbox {NO}\), \(\hbox {Cu}_{3}\hbox {Co}_{3}\hbox {NO}\) and \(\hbox {Cu}_{6}\)CoNO clusters display stronger chemical stability. Magnetic and electronic properties are also discussed. The magnetic moment is affected by charge transfer and the spd hybridization.