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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Crystal structure of the OH-dominant gadolinite-(Y) analogue (Y,Ca)_2(Fe,□)Be_2Si_2O_8(OH,O)_2 from Heftetjern pegmatite, Norway
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Crystal structure of the OH-dominant gadolinite-(Y) analogue (Y,Ca)_2(Fe,□)Be_2Si_2O_8(OH,O)_2 from Heftetjern pegmatite, Norway

机译：来自Heftetjern Pegmatite，挪威的OH-占优势钆 - （Y）模拟（Y，CA）_2（Fe，□）Be_2SI_2O_8（OH，O）_2的晶体结构

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摘要

A hydroxyl-dominant analogue of gadolinite-(Y) (OH-Gad) has been discovered in the Heftetjern granitic pegmatite, southern Norway, in association with late-stage rare-earth-element containing minerals. The empirical formula, based on ten O atoms per formula unit, is (Y_(1.285)Ca_(0.55)Ce_(0.07)La_(0.04)Nd_(0.01))_(Σ1.955)-(Fe_(0.57□0.43)~(2+))Be_(2.02)Si_(1.995)O_(8.48)(OH)_(1.52) . The mineral is monoclinic, space group P2_1/c, a = 4.7514 (10), b = 7.5719 (16), c = 9.9414 (2) ? ,β= 90.015 (4)°, V = 357.663 (3)?~3 and Z = 2. The density calculated using the empirical formula is 3.903 g cm~(-3). The crystal structure was refined to R = 0.0217 for 776 reflections with I > 2σ(I). OH-Gad is isostructural with gadolinite-(Y) and it is characterized by the predominance of OH~- over O~(2-) at the anionic ?-site. The refined crystal-chemical formula is: ~A(Y_(1.25)Ca_(0.55)Ce_(0.2))~X(Fe_(0.57□0.43)~(2+))~ZBe_2- ~TSi_2O_8~?[(OH)_(0.86)O_(0.59)(OH)*_(0.55)] (Z = 2). The possible orientation and local environment of the hydroxyl group were suggested based on bond-valence sum calculations and geometrical analysis of the crystal structure. The infrared spectrum confirms disordering of H atoms. OH-Gad seems to be a potentially new mineral, the first simultaneously hydroxyl- and iron-dominant member of the gadolinite subgroup. It is an OH-analogue of gadolinite-(Y) and an Fe~(2+)- analogue of hingganite-(Y).
机译：在挪威南部南部南部南部南部含有含有矿物质的后期稀土元素的Heftetjern花岗岩（OH-GAD）的羟基占状磷酸盐（OH-GAD）。基于每配方单元的十O原子的经验公式是（Y_（1.285）CA_（0.07）LA_（0.04）ND_（0.01））_（Σ1.955） - （FE_（0.57□0.43） 〜（2 +））be_（2.02）Si_（1.995）O_（8.48）（OH）_（1.52）。矿物是单斜核，空间组P2_1 / C，A = 4.7514（10），B = 7.5719（16），C = 9.9414（2）？ ，β= 90.015（4）°，V = 357.663（3）？〜3和Z = 2.使用经验式计算的密度为3.903g cm〜（-3）。用I>2σ（I）将晶体结构精制到r = 0.0217的776反射。 OH-GAD是具有gadolinite-（Y）的isostrontuctuctucture，其特征在于OH〜-over o-（2-）在阴离子的α- - 层。精制的晶体化学式如下：〜a（y_（1.25）ca_（0.55）Ce_（0.2））〜x（fe_（0.57□0.43）〜（2 +））〜zbe_2-〜tsi_2o_8〜？[（哦） _（0.86）O_（0.59）（OH）* _（0.55）]（Z = 2）。基于粘合价和计算和晶体结构的几何分析，提出了羟基的可能取向和局部环境。红外光谱证实了H原子的障碍。 OH-GAD似乎是一种潜在的新矿物，该矿物的第一个同时同时的羟基 - 和铁亚组亚组。它是Gadolinite-（Y）和Fe〜（2 +）的OH-类似物 - 恒生岩 - （Y）的类似物。

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