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Results for DC.creator="A." AND DC.creator="Altomare" in section 4.2.3 of volume H |
How direct methods work
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.4, pp. 397-399 [ doi:10.1107/97809553602060000957 ]
... There are two basic methods of assigning phases to reflections: (a) Random values between 0 and 360° are assigned to reflections. ... it is possible to solve crystal structures by starting with a large set of phases (more than 40-50) even if ... to seed the phasing process, it is necessary to choose a larger number, which then constitutes the `starting set'. ...
Triplet invariants
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.3, p. 397 [ doi:10.1107/97809553602060000957 ]
... invariants 4.2.3.3. Triplet invariants Triplet invariants (or simply `triplets') play a central role in DM. A probabilistic formula for estimating triplets was first given by Cochran ... for equal atoms and for non-equal atoms, , L is a normalization term depending only on and . The trend ...
Structure invariants
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.2, p. 397 [ doi:10.1107/97809553602060000957 ]
... Structure invariants We now need the concept of structure invariants. A structure factor (whether normalized or not) referred to a new unit-cell origin x0 takes the form , i.e., the ... phase changes according to , while the modulus remains unchanged ( ). A basic question now arises: since the origin can be ...
Normalized structure factors
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.1, pp. 396-397 [ doi:10.1107/97809553602060000957 ]
... diffraction intensities provided by X-ray diffraction experiments are on a relative scale and the normalization process corrects for this as ... at rest and for . From equation (4.2.4) we obtain A plot of the left side of (4.2.5) versus s2 should yield a straight line, for which the intercept with the vertical ...
Direct methods
International Tables for Crystallography (2019). Vol. H, Section 4.2.3, pp. 395-399 [ doi:10.1107/97809553602060000957 ]
... inequalities involving unitary structure factors Uh (see Section 4.2.7 for a definition of Uh). Later Sayre (1952 ) derived Sayre's ... diffraction intensities provided by X-ray diffraction experiments are on a relative scale and the normalization process corrects for this as ... at rest and for . From equation (4.2.4) we obtain A plot of the left side of (4.2.5) versus s2 ...
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.4, pp. 397-399 [ doi:10.1107/97809553602060000957 ]
... There are two basic methods of assigning phases to reflections: (a) Random values between 0 and 360° are assigned to reflections. ... it is possible to solve crystal structures by starting with a large set of phases (more than 40-50) even if ... to seed the phasing process, it is necessary to choose a larger number, which then constitutes the `starting set'. ...
Triplet invariants
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.3, p. 397 [ doi:10.1107/97809553602060000957 ]
... invariants 4.2.3.3. Triplet invariants Triplet invariants (or simply `triplets') play a central role in DM. A probabilistic formula for estimating triplets was first given by Cochran ... for equal atoms and for non-equal atoms, , L is a normalization term depending only on and . The trend ...
Structure invariants
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.2, p. 397 [ doi:10.1107/97809553602060000957 ]
... Structure invariants We now need the concept of structure invariants. A structure factor (whether normalized or not) referred to a new unit-cell origin x0 takes the form , i.e., the ... phase changes according to , while the modulus remains unchanged ( ). A basic question now arises: since the origin can be ...
Normalized structure factors
International Tables for Crystallography (2019). Vol. H, Section 4.2.3.1, pp. 396-397 [ doi:10.1107/97809553602060000957 ]
... diffraction intensities provided by X-ray diffraction experiments are on a relative scale and the normalization process corrects for this as ... at rest and for . From equation (4.2.4) we obtain A plot of the left side of (4.2.5) versus s2 should yield a straight line, for which the intercept with the vertical ...
Direct methods
International Tables for Crystallography (2019). Vol. H, Section 4.2.3, pp. 395-399 [ doi:10.1107/97809553602060000957 ]
... inequalities involving unitary structure factors Uh (see Section 4.2.7 for a definition of Uh). Later Sayre (1952 ) derived Sayre's ... diffraction intensities provided by X-ray diffraction experiments are on a relative scale and the normalization process corrects for this as ... at rest and for . From equation (4.2.4) we obtain A plot of the left side of (4.2.5) versus s2 ...
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