forthcoming articles

The following articles are a selection of those recently accepted for publication in Acta Crystallographica Section A: Foundations and Advances.

See also Forthcoming articles in all IUCr journals.

Accepted 3 August 2021

Combinatorial aspects of the Löwenstein avoidance rule. Part I: the independence polynomial

Practical issues concerning the calculation of independence ratios of finite graphs are analyzed.

Accepted 30 July 2021

Layer groups: Brillouin-zone and crystallographic databases on the Bilbao Crystallographic Server

The set of databases of the Bilbao Crystallographic Server ( including crystallographic data on generators, general positions, Wyckoff positions, maximal subgroups and Brillouin-zone figures and k-vector tables for all 80 layer groups are discussed in detail and illustrated.

Accepted 29 July 2021

The role of an objective function in the mathematical modelling of wide-angle X-ray diffraction curves of semi-crystalline polymers

The choice of an objective function in constructing a mathematical model of an experimental wide-angle X-ray diffraction curve of semi-crystalline polymers is discussed.

Accepted 21 June 2021

X-ray molecular orbital analysis II. Application to diformohydrazide, (NHCHO)2

The molecular orbitals of diformohydrazide were determined by X-ray molecular orbital analysis and it became evident that the molecular orbitals can be obtained by optimizing the electron density observed by X-ray diffraction.

Accepted 18 June 2021

The wavevector star channel and symmetry group

The concepts of `wavevector star channel' and `wavevector star channel group' are newly proposed, which allow the effective study of phase transitions by considering directly the translational symmetry breaking in crystals. It is shown that the complicated symmetry changes in the pyroelectric crystal Pb1−xCaxTiO3 (PCT) can be described using the new five-component reducible order parameter transformed according to the representation of the wavevector star channel group but not the nine-component one based on the theory of the full irreducible representation of the space group.

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