Recently I have solved a crystal structure which gave very good output with R1(Obs data) 2.95%, R1(all data) 4.08%, wR2 0.0698, R(int) 0.0368, R(sigma) 0.0284, Highest peak 0.4300, deepest hole -0.2900. So from the above result it seems that the model is correct and complete. But when I have checked with IUCR online check it shows few alerts.
F(000) Calculated (1024) Reported (570)
Dx(gm cm-3) Calculated (1.683) Reported (1.004)
mu(mm-1) Calculated (1.257) Reported (1.553)
Moiety formula and sum formula matches.
What could be the possible reason?
It looks like if the formula you specified in SHELXL (assuming you are using SHELX) is wrong (not just Z or wrong space group, because the calculated/reported numbers are not commensurate, so it is not just one half, one third etc.). Please check carefully what's your SFAC and UNIT in shelx ins file. Note that this input problems have nothing to do with the quality of the model, which seems satisfactory in fact. What checkcif returns you as "calculated" are properties (mass density, F000, mu etc.) calculated based on the atoms you report in the cif file, which apparently do not coincide with the same properties you also report in the same file (calculated by shelx). That has nothing to do with the model being correct or not, but simply consistent or not. Unit cell size has also no effect, because F000 coincides with the number of electrons in the cell (regardless the dimensions of the cell).
Ok, Thanks to both Piero and Karine for your suggestion. Let me check and get back to you as soon as possible.
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