Can Z, the number of formula units per unit cell, be a fraction? A report of the IUCr Commission on Crystallographic Nomenclature.

IF 1.8 4区材料科学 Q3 CHEMISTRY, MULTIDISCIPLINARY

Acta Crystallographica Section A: Foundations and Advances Pub Date : 2025-09-01 Epub Date: 2025-08-15 DOI:10.1107/S2053273325007053

Carolyn P Brock

引用次数: 0

Abstract

The IUCr Commission on Crystallographic Nomenclature (the CCN) has considered the question of whether fractional values of Z, the number of formula units in the unit cell, can be permitted. The consideration was initiated by a crystallographer who had determined a very unusual molecular structure, but the discussion was later broadened to cover all non-polymeric structures. Reliable structures having a fractional Z were located in the structural databases and in the literature, and were studied carefully. The CCN concluded that in some rare cases the Z value reported for a structure of a stoichiometric compound may be a fraction, but that that choice would have to be justified very carefully and convincingly. For solid solutions Z should be an integer.

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Z，每个单元格的公式单位数，可以是分数吗？国际自然保护联盟晶体学命名委员会的报告。

国际自然保护联盟晶体命名法委员会（CCN）考虑了是否可以允许Z的分数值，即单位胞中公式单位的数目。这个想法是由一位晶体学家提出的，他确定了一种非常不寻常的分子结构，但后来讨论扩大到所有非聚合物结构。具有分数Z的可靠结构位于结构数据库和文献中，并进行了仔细的研究。CCN得出结论，在一些罕见的情况下，化学计量化合物结构的Z值可能是一个分数，但这种选择必须非常仔细和令人信服地证明。对于固溶体Z应该是一个整数。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Acta Crystallographica Section A: Foundations and Advances CHEMISTRY, MULTIDISCIPLINARYCRYSTALLOGRAPH-CRYSTALLOGRAPHY

CiteScore

2.60

自引率

11.10%

发文量

419

期刊介绍： Acta Crystallographica Section A: Foundations and Advances publishes articles reporting advances in the theory and practice of all areas of crystallography in the broadest sense. As well as traditional crystallography, this includes nanocrystals, metacrystals, amorphous materials, quasicrystals, synchrotron and XFEL studies, coherent scattering, diffraction imaging, time-resolved studies and the structure of strain and defects in materials. The journal has two parts, a rapid-publication Advances section and the traditional Foundations section. Articles for the Advances section are of particularly high value and impact. They receive expedited treatment and may be highlighted by an accompanying scientific commentary article and a press release. Further details are given in the November 2013 Editorial. The central themes of the journal are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, periodic, quasiperiodic or amorphous, ideal or real, and, on the other, the theoretical and experimental aspects of the various methods to determine these properties and arrangements.