Hello Everyone,

I am calculating the magnetic moment for a Cobalt cluster which has 6 colbalt atoms. I put this cluster into a 20A supercell as you see in a figure above, constraint lattice parameter (a,b,c) and do the geometry optimization by using Castep code. Here, I had two questions:

1. Is my calculated model correct? One thing I can say that the geometry optimization calculation had been finished with the highest convergence tolerance.

2. After geometry optimization, I also tried to calculate the magnetic moment for whole cluster as explained below:

          In setup tab, I chose Spin polarized, Metal and Use formal spin as initial options. Energy cut off was set to 300eV, Pseudopotentials was Ultrasoft, SCF tolereance was 1.0e-5 ev/atom and All bands/EDFT was chose. However, in k-points tab, I set the the quality medium or fine but the Monkhorst-Pack grid is always 1x1x1. I don't know what is reason. Moreover, I also modified the grid parameters to 9x9x1 but results didn't make any differences.

          When energy calculation tasks included Band structure, Density of States calculation finished . I used the Castep analysis package to deduced the Spin moment value for all 6 cobalt atoms as below:

         Analysis Density of States for the d orbial only. Display DOS was chose to be Spin and Function was intergrated DOS. And then I got a graph named the Castep Partial Number of States graph. As my understand, the magnetic moment of the cluster will be equal to a value at Fermi Level. In this case, my result was about 14.65885724 uB.

         I made a comparision with other papers but my result is slightly different, for instance result of magnetic moment of Cobalt 6 cluster is 13.68 uB the PHYSICAL REVIEW B 67, 174413 ,2003 and 12.96 uB in the Chemical Physics 354 (2008) 196–201. I am very confused about my result. Therefore, I would like to ask every people whether my result is reliable?

Thanks

LeVu