QUESTIONNAIRE FOR the
STRUCTURE DETERMINATION BY POWDER DIFFRACTOMETRY ROUND ROBIN - 2
Please answer all questions as completely as possible. Provide
one filled questionnaire for each data (samples 1, 2 and 3).
Forward the results no later than Sunday 24th November 2002 to :
Lachlan M.D. cranswick
Collaborative Computational Project No 14 (CCP14) for Single
Crystal and Powder Diffraction.
by email : L.M.D.cranswick@dl.ac.uk (dl for Daresbury Laboratory).
Preferably, attach the results as one PDF file or as a MS Word
document compressed by Winzip.
It is advised to complete the form as the structure determination
progress.
0.1 Is the first sample structure solvable with this quality
of data ? Yes [ ] No [ ]
0.2 Is the second sample structure solvable with this quality
of data ? Yes [ ] No [ ]
0.3 Is the third sample structure solvable with this quality
of data ? Yes [ ] No [ ]
0.3 If not, what data would be required ?
Then, for each sample :
1. Preliminary work
1.1 Did you obtained additional informations from the
chemical formula ? If yes, how and what information ?
(for instance from CSD or ICSD or ICDD databases)
1.2 Did you obtained additional informations from the
powder pattern ? If yes, how and what information ?
(for instance using the JCPDS-ICDD database)
1.3 Did you extract the structure factors ? Yes [ ] No [ ]
1.3.1 If yes, which program(s) did you use ?
1.3.2 Give the angular range:
1.3.3 Give the number of extracted structure factors:
1.3.4 Give the Rp and Rwp (conventional Rietveld, background subtracted):
1.3.5 Give the Rp and Rwp (background not subtracted):
1.3.6 If not, did you use the whole pattern ?
1.3.7 Or a partial pattern (if yes, give the angular range):
2- Structure solution
2.1 Did you use direct methods ? Yes [ ] No [ ]
2.1.1 If yes, was it on the whole dataset ?
2.1.2 Or on a partial dataset ?
2.1.3 Give the number of reflections:
2.1.4 Which program(s) did you use ?
2.1.5 Did you modified intensities of closely neighbouring
reflections ? If yes, explain how.
2.2 Did you use Patterson methods ? Yes [ ] No [ ]
2.2.1 If yes, was it on the whole dataset ?
2.2.2 Or on a partial dataset ?
2.2.3 Give the number of reflections:
2.2.4 Which program(s) did you use ?
2.2.5 Did you modified intensities of closely neighbouring
reflections ? If yes, explain how.
2.3 Did you use another method ? Yes [ ] No [ ]
2.3.1 If yes, which method(s) (give details : molecule location
by direct space - genetic algorithm, Monte Carlo, Simulated
anneling, scratch, other) ?
2.3.2 Which program(s) did you use ?
2.3.3 If you used molecule location methods, how many independent
molecules did you use (give details on these molecules)? How
many degrees of freedom (total) ? How many torsion angles ?
2.4 Did you first locate the whole structure ? Yes [ ] No [ ]
2.4.1 If not, how many atoms did you locate ?
2.4.2 Give their name and initial atomic coordinates
Atom x y z
................................
................................
................................
2.4.3 Were the initial atomic coordinates taken from a known
structure ? Yes [ ] No [ ]
If yes, which one (give reference) ?
3- Structure completion
3.1 Did you performed Fourier difference syntheses before
refining the structure by the Rietveld method ? Yes [ ] No [ ]
3.2 If yes, with what program ?
3.3 If yes, how many additional atoms did you obtained from Fourier
difference syntheses ?
3.4 Give their name and atomic coordinates as they were obtained
Atom x y z
.................................
.................................
.................................
3.5 Did you made first Rietveld refinements without preliminary
Fourier difference syntheses ? Yes [ ] No [ ]
3.5.1 If yes, with what program ?
3.5.2 What were the Rp and Rwp (background subtracted AND not
subtracted) and RB and RF that you obtained at the first
Rietveld application ?
3.5.3 Did you get the structure factors from this result and
performed a Fourier difference synthesis ?
3.5.4 Did you locate additional atoms at this stage ?
3.5.5 And which one ?
Atom x y z
.................................
.................................
.................................
3.5.6 If you repeated Rietveld refinements and Fourier synthese
several times before to complete the model, give the number
of times and which atoms you locate and the Rp, Rwp
RB, RF at each times.
Atom x y z
.................................
.................................
.................................
4- Final refinement
- Give the final atomic coordinates, thermal parameters,
standard deviations, Reliability factors...........
Atom x y z B
...........................................
...........................................
...........................................
- Give details about constraints, restraints
5- Feel free to add any intermediate results (list of extracted structure
factors, software decisive input and output data...) or comments you
might consider as essential (details on hardware, time for solving the
structure, number of moves by Monte Carlo or molecule position trial,
any picture...).
Lachlan has large disk space.