Thank you all very much for the immediate help.

One more question, may I???

What can the minimum kmax be?

I think it can be about 8 according to Scott.

If I use kmin=2, can it be 7 or 6? The reason why I ask this is that when I plot R space with my sample, which has been reduced and needs to be confirmed if there is any metal cluster, the metal peak shows at kmax=8, but it disappears at kmax=6 or 7. At kmax=10, it is hard to tell because the spectrum is very noisy (it shows split peak). When there are extremely small metal clusters (even at CN=0.6), I can see a distinct metal peak that does not change no matter what k range and weight I use. I wonder any further advice can be suggested. 

Thank you for your help in advance.

Steven