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arXiv 1007.0119cond-mat.mtrl-sci
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高压下ThGeO4的实验和理论研究

Experimental and theoretical investigations on ThGeO4 at high pressure

D. Errandonea, Ravhi. S. Kumar, L. Gracia, A. Beltran, S. N. Achary, A. K. Tyagi

摘要:

在这里,我们报告的角度色散X射线衍射实验进行ThGeO 4高达40 GPa和总能量密度功能理论计算的综合结果。在11 GPa压力下,锆型ThGeO 4发生了相变,转变为四角白钨矿结构。第二个相变的单斜M-fergusonite型被发现超过26 GPa。在环境压力下在白钨矿相中结晶的样品中观察到了相同的转变。没有额外的相变或分解的ThGeO 4的证据已被检测到高达40 GPa。单斜高压相的晶胞参数为a = 4.98(2)A,b = 11.08(4)A,c = 4.87(2)A,β = 90.1(1),Z = 4(28.8GPa)。白钨矿-辉砷铅矿的转变是可逆的,而锆石-白钨矿的转变是不可逆的。通过实验和计算,得到了不同相的室温状态方程。根据Th-O键和Ge-O键的微分压缩性讨论了所研究晶体的各向异性压缩性。

英文摘要:

We report here the combined results of angle-dispersive x-ray diffraction experiments performed on ThGeO4 up to 40 GPa and total-energy density-functional theory calculations. Zircon-type ThGeO4 is found to undergo a pressure-driven phase transition at 11 GPa to the tetragonal scheelite structure. A second phase transition to a monoclinic M-fergusonite type is found beyond 26 GPa. The same transition has been observed in samples that crystallize in the scheelite phase at ambient pressure. No additional phase transition or evidence of decomposition of ThGeO4 has been detected up to 40 GPa. The unit-cell parameters of the monoclinic high-pressure phase are a = 4.98(2) A, b = 11.08(4) A, c = 4.87(2) A, and beta = 90.1(1), Z = 4 at 28.8 GPa. The scheelite-fergusonite transition is reversible and the zircon-scheelite transition non-reversible. From the experiments and the calculations, the room temperature equation of state for the different phases is also obtained. The anisotropic compressibility of the studied crystal is discussed in terms of the differential compressibility of the Th-O and Ge-O bonds.

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