How can I create a correct model for a nano cluster ?

Dear alls,

I am planning to calculate the magnetic property for gold nano cluster by using Castep code. I used the nano cluster tool to create one 4A  gold cluster. After that, I created a surface P1 and build 12A vacuum slab. I used castep to calculate but the results was not similar according to some paper! I wonder whether I have built the correct model.

Please help me.

Thanks and Regards,

vuphotonic.