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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Synthesis and proposed crystal structure of a disordered cadmium arsenate apatite
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Synthesis and proposed crystal structure of a disordered cadmium arsenate apatite

机译：无序砷酸镉磷灰石的合成及晶体结构

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During a study into the synthesis of minerals composed of mining wastes aimed at improving their immobilisation,a cadmium arsenate apatite has been prepared by hydrothermal methods.The structure of this apatite was analysed by single crystal X-ray diffraction,and was found to consist of a standard apatite framework based on CD_3(AsO_4)_3X,where X represents an anion resident on the(0,0,0.25)site.The framework is hexagonal with the space group(no 176),a = 9.9709(8),c-6.4916(4)A.The X ion site is predominantly occupied by Cl~ ions;however due to significant shortening of the c axis exhibited by all cadmium containing apatite phases,a pure chlorapatite is not possible without a significant cation deficiency.No evidence of the necessary deficiency was found in the crystal structure.For larger bromo-and iodo-apatites significant modulations along the c-axis are required to accommodate the halide.This paper examines a number of compensation mechanisms and proposes that a minor disorder of chloride,oxide and hydroxide located on the X ion site provides the required charge compensation mechanism.This is contrary to previous complex modulations proposed in the literature.The proposed chemical formula is Cd_5(AsO_4)_3Cl_(1-2x-y)O_x(square)_xOH,where D represents a vacancy.
机译：在研究旨在改善固定化作用的矿山废料组成的矿物的合成过程中，通过水热法制备了砷酸镉磷灰石。通过单晶X射线衍射分析了该磷灰石的结构，发现其组成为一个基于CD_3（AsO_4）_3X的标准磷灰石框架，其中X表示驻留在（0,0,0.25）位置上的阴离子。该框架为六边形，空间组为（no 176），a = 9.9709（8），c -6.4916（4）A.X离子位点主要被Cl〜离子占据;但是由于所有含镉的磷灰石相均表现出c轴的显着缩短，因此如果没有明显的阳离子缺乏，纯净的磷灰石是不可能的。对于较大的溴和碘磷灰石，需要沿c轴进行较大的调制才能容纳卤化物。本文研究了许多补偿机制，并提出了少量的ch失调。 X离子位点上的卤化物，氧化物和氢氧化物提供了所需的电荷补偿机制，这与文献中先前提出的复杂调制相反。拟议的化学式为Cd_5（AsO_4）_3Cl_（1-2x-y）O_x（square ）_xOH，其中D表示空位。

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