The most incompressible metal osmium at static pressures above 750 gigapascals
The most incompressible metal osmium at static pressures above 750 gigapascals
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DOI：
10.1038/nature14681
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发表时间：
2015-09-10
期刊：
影响因子：
64.8
通讯作者：
Abrikosov, I. A.
中科院分区：
文献类型：
--
作者：
Dubrovinsky, L.;Dubrovinskaia, N.;Abrikosov, I. A.
金属Os(Os)是最特殊的元素材料之一，在常压下具有已知的最高密度，以及最高的结合能和熔化温度(1)。它也是非常不可压缩的(2-4)，但它的高压行为还没有被很好地理解，因为到目前为止，人们只在75千兆帕以下的压力下对它进行了研究(2-6)。在这里，我们报道了用常规和双级金刚石顶压室(7)在几兆巴压力下对Os进行粉末X射线衍射测量(7)，通过首先在高达500千兆帕的静态实验中获得金、铂和钨的自洽状态方程来确保准确的压力测量。这些测量结果表明，在压缩到770亿级以上时，Os仍保持其六方密排结构。但是，尽管其摩尔体积随着压力的增加而单调减小，但Os的晶胞参数比在大约150亿帕斯卡和440吉帕斯卡处表现出反常。动力学平均场理论计算表明，前者的反常是价电子费米面拓扑变化的标志。然而，440千兆帕斯卡的异常可能与核心电子之间的压力诱导相互作用相关的电子跃迁有关。在静态高压实验条件下影响核心电子的能力，即使是像Os这样的不可压缩金属，也为在极端压缩下寻找物质的新状态打开了机会。
Metallic osmium (Os) is one of the most exceptional elemental materials, having, at ambient pressure, the highest known density and one of the highest cohesive energies and melting temperatures(1). It is also very incompressible(2-4), but its high-pressure behaviour is not well understood because it has been studied(2-6) so far only at pressures below 75 gigapascals. Here we report powder X-ray diffraction measurements on Os at multi-megabar pressures using both conventional and double-stage diamond anvil cells(7), with accurate pressure determination ensured by first obtaining self-consistent equations of state of gold, platinum, and tungsten in static experiments up to 500 gigapascals. These measurements allow us to show that Os retains its hexagonal close-packed structure upon compression to over 770 gigapascals. But although its molar volume monotonically decreases with pressure, the unit cell parameter ratio of Os exhibits anomalies at approximately 150 gigapascals and 440 gigapascals. Dynamical mean-field theory calculations suggest that the former anomaly is a signature of the topological change of the Fermi surface for valence electrons. However, the anomaly at 440 gigapascals might be related to an electronic transition associated with pressure-induced interactions between core electrons. The ability to affect the core electrons under static high-pressure experimental conditions, even for incompressible metals such as Os, opens up opportunities to search for new states of matter under extreme compression.