Density functional calculations of polysynthetic Brazil twinning in α-quartz.

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-05-01 Epub Date: 2012-03-22 DOI:10.1107/S0108767312008756

Hans Grimmer, Bernard Delley

引用次数: 3

Abstract

Polysynthetic Brazil twinning in α-quartz, which occurs commonly in amethyst, is interpreted in the literature as having its composition planes parallel to one of the faces of the major rhombohedron r. It is shown that, instead, the composition planes are parallel to one of the faces of the minor rhombohedron z. The proposed translation 0.4547a between neighbouring lamellae leads to binding distances and binding angles across the composition plane that differ less from their bulk values than for the translation 0.5a proposed in the literature. Density functional calculations show that the energy of the unrelaxed polysynthetic twin is lower for the proposed translation. They also show that relaxation increases the thickness of the polytwin by 4 pm per composition plane.

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α-石英中聚合成巴西孪晶的密度泛函计算。

α-石英中的聚合成巴西孪晶，常见于紫水晶中，在文献中被解释为其组成面平行于主菱形体r的一个面。合成平面平行于小菱形体z的一个面。相邻片片之间提出的平移0.4547a导致合成平面上的结合距离和结合角与其体积值的差异小于文献中提出的平移0.5a。密度泛函计算表明，对于所提出的平移，非松弛聚合成孪晶的能量较低。他们还表明，弛豫使聚孪晶的厚度在每个合成平面上增加了4pm。

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 化学-晶体学

自引率

11.10%

发文量

审稿时长

3 months

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.