The structure and magnetic properties of Os_𝑛B(𝑛 = 11–20) clusters have been systematically investigated by using density functional theory within the generalized gradient approximation (GGA). For each size, the average binding energy per atom, the second-order differences of total energies, the dissociation energies and the formation energies are calculated to analyse the stability of clusters. Os₁₂B, Os₁₅B, Os₁₇B and Os₁₉B clustersare found to be more stable than other clusters. The B atom has little influence on Os_𝑛B cluster stability. d electrons exhibit locality compared to s and p electrons in most cases. Os₁₄B cluster has the strongest magnetism among all the clusters, and the local magnetic moment of B atom does little effect to the total magnetic moment.

A theoretical study of NO adsorption on Cu$_m$Co$_n$ ($2 \leq m + n \leq 7$) clusters was carried out using a densityfunctional method. Generally, NO is absorbed at the top site via the N atom, except in Cu$_3$NO and Cu$_5$NO clusters,where NO is located at the bridge site. Co$_2$NO, Co$_3$NO, Cu$_2$Co$_2$NO, Co$_5$NO, Cu$_2$Co$_4$NO and Cu$_6$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. Cu$_2$CoNO, Cu$_3$CoNO, Cu$_2$Co$_2$NO, Cu$_3$Co$_3$NO and CuCo$_5$NO clusters are more stable than their neighbours, while CuCoNO, Co$_3$NO, Cu$_3$CoNO, Cu$_2$Co$_3$NO, Cu$_3$Co$_3$NO and 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.