Thanks Carlo and Scott for ur response. Some numbers from my fits in this regard and some more queries. When I make a cluster based on the Alumina structure (replacing the central Al with Y with relaxed lattice parameters) I get DW 0.0025 +- 0.002, without any restraint. While I restrain the DW to 0.005, my CN jumps from 4.8 to 5.2. When I make a cluster based on Yttria structure, I get DW factor of 0.008 +- 0.002, unrestrained. While I restrain the DW to 0.01, it again jumps from 4.8 to 5.2. First query...if you can pin down on the CN change (Carlo..you wanted some numbers) Second...what are ur comments on the above 2 models and the change in DW factors. I might add that ther is no appreciable difference with k=2, 3 or 2&3 fittings. All the fits produce red-chi-sqr less than 100 (~50-70), all R-factors are <0.01 and no unphysical reports after the fit. And I have only 1 peak to worry about, there is no second shell correlation seen. I would appreciate your 2 cents on this. Warm regards Shan -- ||||||||||||||||||||||||||||||||| Shantanu Behera Center for Advanced Materials and Nanotechnology Lehigh University 5, East Packer Avenue Bethlehem, PA 18015, USA