A new high-pressure and high-temperature polymorph of FeS
A new high-pressure and high-temperature polymorph of FeS
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DOI：
10.1007/s00269-007-0151-0
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发表时间：
2007-03
影响因子：
1.4
通讯作者：
H. Ohfuji;N. Sata;H. Kobayashi;Y. Ohishi;K. Hirose;T. Irifune
中科院分区：
文献类型：
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作者：
H. Ohfuji;N. Sata;H. Kobayashi;Y. Ohishi;K. Hirose;T. Irifune
在激光加热的金刚石砧细胞中，通过原位同步x射线衍射测量，在压力大于30 GPa、温度为1300 K的条件下，观察到一种新的FeS晶型。它在1300 K下至少稳定到170 GPa。新相（这里称为FeS VI）在85 GPa和300 K下具有正交晶胞，晶格参数为sa= 4.8322 （17） Å，b= 3.0321 (6) Å， c= 5.0209 (8) Å。它的拓扑框架基于nias型结构，与其他已报道的多晶型（FeS I-V）一样。然而，FeS VI的单元胞在原nias型胞的[010]方向上有更多的扭曲（收缩）。例如，在85 GPa和300 K下，c/轴比为~ 1.66，大大小于正交型FeS II（~ 1.72）和nias型六方FeS V（=√3≈1.73）。FeS IV和VI之间的相边界预计位于1300k下的30gpa左右。相变伴随着体积和轴比的逐渐和连续的变化，可能是二级的。在室温下，当压力高于36gpa时，FeS VI比FeS III变得稳定。因此，FeS III-VI和/或FeS IV-VI的相界具有负压依赖性。
A new polymorph of FeS has been observed at pressures above 30 GPa at 1,300 K by in situ synchrotron X-ray diffraction measurements in a laser-heated diamond anvil cell. It is stable up to, at least, 170 GPa at 1,300 K. The new phase (here called FeS VI) has an orthorhombic unit cell with lattice parametersa= 4.8322 (17) Å,b= 3.0321 (6) Å, andc= 5.0209 (8) Å at 85 GPa and 300 K. Its topological framework is based on the NiAs-type structure as is the case for the other reported polymorphs (FeS I-V). The unit cell of FeS VI is, however, more distorted (contracted) along the [010] direction of the original NiAs-type cell. For example, thec/baxial ratio is ∼1.66 at 85 GPa and 300 K, which is considerably smaller than that of orthorhombic FeS II (∼1.72) and NiAs-type hexagonal FeS V (=√3 ≈ 1.73). The phase boundary between FeS IV and VI is expected to be located around 30 GPa at 1,300 K. The phase transition is accompanied by gradual and continuous changes in volume and axial ratios and may be second order. At room temperature, FeS VI becomes stable over FeS III at pressures above 36 GPa. It is, therefore, suggested that the phase boundary of FeS III–VI and/or FeS IV–VI has negative pressure dependence.