Dear Colleagues, I need your expert point of view on the complex problem associated with the thermal parameters.
Description: New crystal structure contained Ba, Ca, K, P,O elements (with some Mn,Eu dopants) was solved and refined using Topas 4.2. The Checkcif tool found only a few Alert C, namely: Low ’MainMol’ Ueq as Compared to Neighbors of P1. The thermal parameters Biso of Ba ion are in the range of 1.52(8)-2.84(5) A^2, Biso(Ca)= 2.5(2)A^2, Biso(K) = 1.1(1) A^2, Biso(P)=1.52(6) A^2, O ions have 3.2(1) A^2 (one parameter for all O ions). There are 15 independent ions in the asymmetric cell. The pattern was measured using CuKa in the range of 5-140 deg. Max. Intensity ~200.000 Cps. The Problem: The Reviewer wrote that the suggested crystal structure was less than satisfactory because Biso should be less that 0.7A^2 for cations and less than 2A^2 for oxygens. The similar published structure with the same problem: I have found the cif-file of the similar structure Ba2CaNa3(PO4)3, which was solved/refined using single crystal method, that Biso(Ba) are in the range of 1.58-1.75 A^2 which is much bigger than 0.7 A^2 and the Biso(O) values vary in the range of 1.42-4.3 A^2. So, I have the questions: -Where can I get the reliable information about the trustful range for thermal parameters? -Who and why decides to involve these maximal values 0.7 A^2 for heavy ions and 2A^2 for oxygen ions. Maybe do you know the relevant manuscript? -Whether the Ba2CaNa3(PO4)3 structure [Kim, M., Kobayashi, M., Kato, H., Yamane, H., Sato, Y., & Kakihana, M. (2015). Dalton Transactions, 44(4), 1900-1904] with so "big" thermal parameter also was solved/refined using single crystal experiment less than satisfactory? I think the problem will arise several times in the future and answers will be a great help to many subscribers here. Sorry for long text. Best wishes, Maxim
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