Oops sorry for the slippery fingers. I meant h00, 0k0 and 00l in my original email and NOT "00h, 00k, 00l". Note the correction especially if you are a first-year graduate student trying to learn stuff from these emails :)

Raji



On Thu, Jul 7, 2011 at 11:30 PM, Raji Edayathumangalam <[log in to unmask]> wrote:
Hello Everyone,

I have a 3.1 Ang dataset for which I'd like to get to the bottom of what the correct space group is.

The current unit cell in p212121 is 98.123   101.095   211.201    90.000    90.000    90.000
I fed the reflection data into Xtriage to look for twinning and pseudotranslational NCS and there is no indication for either issue in the Xtriage output. Also, all odd 00h, 00k, 00l reflections are systematically absent as they should be for p212121.

However, my colleague who is also working on the same dataset recently reprocessed the data in P21. Here's the cell in p21:
98.010  100.940  210.470  90.00  90.04  90.00 p21

I am not sure if BETA=90.04 is significant enough to treat as p21 (0.04% deviation of beta angle from ideal lattice for p212121). I don't think so but I could be wrong. Could someone please clarify?

Also, what kind of twinning and twinning operators can relate a p212121 cell to a p21 cell with almost identical unit cell parameters as that of the p212121 cell and leave all systematic absences intact?

Thanks much.
Raji


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Raji Edayathumangalam
Instructor in Neurology, Harvard Medical School
Research Associate, Brigham and Women's Hospital
Visiting Research Scholar, Brandeis University




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----------------------
Raji Edayathumangalam
Instructor in Neurology, Harvard Medical School
Research Associate, Brigham and Women's Hospital
Visiting Research Scholar, Brandeis University