霞石NaAlSiO_4的压缩性及其机理研究  

Investigation on the Compressibility of Nepheline NaAlSiO_4 and Its Mechanism

作　　者：牛菁菁[1] 巫翔[1] 秦善[1] 翟双猛[2] 杨科[3] NIU Jmg-jing;WU Xiang;QIN Shan;ZHAI Shuang-meng;YANG Ke(Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Science, Peking Universtiy, Beijing 100871, China;Institue of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;Shanghai Institute of Applied Physcis Chinese Academy of Sciences, Shanghai Synchrotron Radiation Facility, Shanghai 201204, China)

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]中国科学院地球化学研究所,贵阳550002 [3]中国科学院上海应用物理研究所,上海201204

出　　处：《矿物岩石地球化学通报》2017年第5期850-854,共5页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(U1232204;41473056)

摘　　要：NaAlSiO_4高压相CF相的结构和性质近年来被广为关注,然而对其低压相霞石的高压行为研究并不深入。为进一步认识碱金属在CF相中的赋存状态,采用金刚石压腔和同步辐射X射线衍射,开展了霞石NaAlSiO_4(P63,Z=8)常温、20GPa时的压缩性质研究。结果显示,在实验压力范围内,霞石没有发生结构相变,其三阶等温状态方程参数为:V0=0.715(2)nm^3,K0=53(3)GPa,K'=4.1(3),a和c轴的压缩系数Ka=3.8(1)×10^(-3)nm/GPa,Kc=2.42(6)×10^(-3)nm/GPa。通过第一性原理计算模拟,印证了实验压缩性的结果,揭示了霞石的压缩机制,即SiO_4和AlO_4四面体呈刚性行为,这些四面体之间的扭转导致结构中伪正交空隙通道的畸变。CF phase（ NaAlSiO_4） ＇s structure and physical properties has attracted a wide attention,however,the high pressure behavior of nepheline is quite unclear. For further understanding on the occurrence of the alkali metal in CF phase,investigation on the compressibility of nepheline NaAlSiO_4（ P63,Z = 8） at room temperature with pressure up to20GPa has been carried out by using diamond anvil cell and synchrotron X-ray diffraction. No phase transition of nepheline occurs in present experimental conditions,and its parameters of isothermal equation of state are V0= 0. 715（ 2） nm^3,K0= 53（ 3） GPa,K＇ = 4. 1（ 3）. The compressional coefficients are 3. 8（ 1） × 10^-3nm/GPa for the a axis and 2. 42（ 6） ×10^-3nm/GPa for the c axis,respectively. The results from first-principle calculations not only underpin the experimental observations,but also reveal the compressional mechanism of nepheline,i.e. the rigid behavior of SiO_4 and AlO_4 tetrahedron,and their tilting resulting in the distortion of pseudo-orthogonal channel alone the c-axis direction.

关 键 词：霞石NaAlSiO4 压缩性 金刚石压腔 X射线衍射 第一性原理计算 

分 类 号：P578.972[天文地球—矿物学]