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Twinning dictionary version 1.0
Category TWIN_REFLN
Name:'_twin_refln_[]'
Definition:
Items in the TWIN_REFLN category tabulate the calculated values of F^2^
for each peak observed in the diffraction pattern,
together with the measured value of F^2^.
The calculated F^2^ for an observed peak is a weighted sum
of the contribution of all the twin components.
The calculated structure factor for each twin contribution can also
be given.
Examples:
This partial listing describes seven observed diffraction peaks
in a four-individual twin by non-merohedry. The reference individual
is 1. Reflections from the other three individuals 2, 3 and 4 are
present only if these cannot be experimentally separated from the
reference individual.
loop_
_twin_refln_datum_id
_twin_refln_individual_id
_twin_refln_index_h
_twin_refln_index_k
_twin_refln_index_l
_twin_refln_F_squared_meas
_twin_refln_F_squared_sigma
_twin_refln_include_status
1 1 1 0 0 1.03 0.18 o
1 3 1 0 0 1.03 0.18 o
2 1 2 0 0 1290.01 55.59 o
2 3 2 0 0 1290.01 55.59 o
3 1 3 0 0 2.59 0.42 o
3 3 3 0 0 2.59 0.42 o
4 1 4 0 0 30.98 1.47 o
4 3 4 0 0 30.98 1.47 o
5 1 5 0 0 1.97 0.96 o
5 3 5 0 0 1.97 0.96 o
6 1 6 0 0 1.55 1.14 o
6 2 6 1 2 1.55 1.14 o
6 3 6 0 0 1.55 1.14 o
6 4 6 1 2 1.55 1.14 o
7 1 -6 1 0 0.47 1.06 o
7 2 6 2 2 0.47 1.06 o
|
This example is taken from Colombo Young & Gladfelter
[Inorg. Chem. (2000), 39, 4621-4624].
Two structures of nitronium tetranitratogallate
are reported as a result of an enantiotropic phase transition.
The higher-temperature phase is in the tetragonal space group I-4,
while the lower-temperature phase is a twin by non-merohedry
in space group I2.
The individuals are enantiomorphic as a result of the phase transition.
In the listing it is clear that datums 620-624 do not contain
overlapping reflections, whereas datums 625-629 contain contributions
from both twins.
loop_
_twin_refln_datum_id
_twin_refln_individual_id
_twin_refln_index_h
_twin_refln_index_k
_twin_refln_index_l
_twin_refln_F_squared_calc
_twin_refln_F_squared_meas
_twin_refln_F_squared_sigma
_twin_refln_include_status
620 1 1 -6 -3 200.22 207.88 3.35 o
621 1 -1 6 3 225.34 224.15 3.62 o
622 2 -1 6 3 184.64 196.34 3.95 o
623 1 -1 -6 -3 173.28 181.13 3.06 o
624 2 -1 -6 -3 143.40 152.05 2.78 o
625 1 1 6 3 204.45 204.38 4.48 o
625 2 3 -6 1 204.45 204.38 4.48 o
626 1 3 -6 -3 240.97 241.19 3.75 o
626 2 -3 6 3 240.97 241.19 3.75 o
627 1 3 6 3 288.54 281.53 4.31 o
627 2 -3 -6 -3 288.54 281.53 4.31 o
628 1 -5 -6 -3 179.56 176.35 5.36 o
628 2 -3 6 5 179.56 176.35 5.36 o
629 1 5 6 3 235.04 238.84 4.06 o
629 2 -5 -6 -3 235.04 238.84 4.06 o
|
Type: null
Category: category_overview