摘要
采用同步辐射光源和金刚石对顶砧（DAC）技术,对天然菱铁矿的压缩性和电子结构进行了原位X射线衍射（XRD）和X射线吸收近边结构谱（XANES）测试研究。在室温下随着压力逐渐升高至50.2 GPa,菱铁矿保持方解石型结构不变,但是逐渐向Na Cl型结构转变;刚性[CO3]^2-基团平行于ab-平面定向排列使c轴的压缩性大于a轴。菱铁矿在44.6～47.1 GPa之间发生电子由高自旋态（HS）向低自旋态（LS）的转变,表现为体积塌陷8%。HS菱铁矿的等温状态方程参数为K0=112（5）GPa和K＇0=4.6（3）。首次采用XANES技术对菱铁矿中Fe^2＋的电子结构进行了研究,结果表明：随着压力升高至37.3 GPa,Fe^2＋的配位和局域对称并未发生明显变化;此后电子结构开始转变,Fe^2＋的3d轨道分裂能降低,电子跃迁概率增大,呈现LS特性。
In situ synchrotron radiation X-ray diffraction（ XRD） and X-ray absorption near edge structure（XANES） measurements were employed to investigate the compressibility and the electronic structure of natural siderite in diamond anvil cells（ DACs）. No phase transition occurs up to 50. 2 GPa at room temperature but a pressure-induced structure evolution from the calcite-type to the Na Cl-type can be observed. The axial compression is anisotropic with c-axis more compressible than a-axis. Fe^2＋undergoes spin state transition（ HS→LS） at 44. 6 ~47. 1 GPa with volume collapse 8%. Fitting to the Brich-Murnaghan equation of state yields bulk modulus K0= 112（5） GPa and its pressure derivative K＇0= 4. 6（3）. XANES measurement was used for the first time to investigate the electronic structure of Fe^2＋in siderite. The result implies that no major changes take place in the coordination and the local symmetry of Fe^2＋until 37. 3 GPa; thereafter the HS→LS transition occurs and the LS Fe^2＋has lower splitting energy and higher probability of electronic transition.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2016年第2期276-282,共7页
Acta Petrologica et Mineralogica
基金
国家自然科学基金资助项目(U1232204,41473056)
关键词
菱铁矿
自旋转变
金刚石压腔
X射线衍射
X射线吸收近边结构谱
siderite
spin state transition
diamond anvil cell（DAC）
X-ray diffraction（XRD）
X-ray absorption near edge structure（XANES）
