Metallic Properties of the Isotopes of Hydrogen

氢原子是由一个质子和一个电子结合在一起组成的。 氘原子核是由一个质子和一个中子组成的，所以质量是氢的两倍。本研究的目的是研究氢同位素的性质：氢，氘和金属相中的氘化氢（氚因具有放射性而被省略），统称为氢。 一般来说，元素的同位素效应很小，只有百分之一到百分之二。在氢中，D2与H2的质量比为200%，对性能的影响可能非常大。例如，氢的一个重要量子方面是凝聚态相的零点能量或运动。结果是，在零温度极限下，原子或分子在晶格位置上不是固定的位置，而是围绕这些位置运动。 这种材料具有非常低的固化温度（分子氢，约14 K;氘约18 K）。氦比氢分子更量子化，并且没有固态，在T= 0 K时仍保持液态。 原子氢本身被预测具有液态基态。研究小组计划研究高压对氢的影响。该团队已经通过实验证明，氘化氢是一种稳定的分子，在~200 GPa的压力下变得不稳定，解离和重组形成HD，D2和H2的稳定混合物。因此，在这项研究中，同位素在超高压和低温下的性质将被研究。技术摘要研究计划是研究氢在压力下的性质，在那里它们是金属。在研究计划中，已经表明氢在~500 GPa下变成金属。预期氘的压力将更高，因为由于其更大的质量，分子氘将具有更小的零点能量和更大的结合能。 HD应该有很多惊喜，因为在~200 GPa以上，它变成了0.5 HD和0.25（H2+D2）的混合物。可能需要500 GPa的压力来解离H2分子，但HD可能在更低的压力下变得不稳定。在这项研究中预计会有惊喜。一旦同位素被金属化，基态将通过X射线分析进行研究。对氢的一个有趣的预测是，它可能是一种室温超导体，这将被研究。它也被预测为亚稳态，即当压力释放时，它可以保持在金属状态。应通过在低温下降低压力，然后升高温度直至样品转化回分子相来研究同位素的亚稳性。 氢可能不是亚稳态的，但氘是，因为它的零点能量较小。最后，还将制定一个用于监测压力的压力表。在500+GPa下没有好的尺度。 对氮空位纳米金刚石中荧光线偏移的研究可以产生一种新的压力校准标度。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical AbstractThe hydrogen atom is composed of a single proton and a single electron bonded together. The deuterium nucleus is composed of a proton and neutron, so twice the mass of hydrogen. The objective of this research is to study the properties of the hydrogen isotopes: hydrogen, deuterium, and hydrogen deuteride in the metallic phases (tritium is omitted as it is radioactive), collectively referred to as the hydrogens. In general isotopic effects of elements are small, of order a percent or two. In the hydrogens, the mass ratio of D2 to H2 is 200% and the impact on the behavior can be very large. For example, one of the important quantum aspects of hydrogen is the zero-point energy or motion in the condensed matter phase. The consequence is that in the zero temperature limit, the atoms or moleules are not in fixed positions in lattice sites, but have motion around these sites. Such materials have very low temperatures of solidification (molecular hydrogen, about 14 K; deuterium about 18 K). Helium is even more quantum than the molecular hydrogens and does not have a solid state, remaining liquid to T= 0K. Atomic hydrogen itself is predicted to have a liquid ground state. The research team plans to study the effects of high pressure on the hydrogens. The team has already shown experimentally that hydrogen deuteride, which is a stable molecule, becomes unstable at a pressure of ~200 GPa, dissociating and recombining to form a stable mixture of HD, D2 an H2. Thus, in this research the properties of the isotopes at ultra high pressures and low temperatures shall be studied.Technical AbstractThe program of research is to study the properties of the hydrogens at pressure where they are metallic. In the research program it has already been shown that hydrogen becomes a metal at ~500 GPa. It is expected that the pressure will be higher for deuterium as, due to its larger mass, molecular deuterium will have smaller zero-point energy and a larger binding energy. HD should have many surprises as above ~200 GPa it becomes a mixture of 0.5 HD and 0.25 (H2+D2). It may require a pressure of 500 GPa to dissociate the H2 molecules, but the HD may become unstable at still a lower pressure. Surprises are expected in this study. Once the isotopes are metallized, the ground state will be studied by xray analysis. One of the intriguing predictions for hydrogen is that it may be a room temperature superconductor, which will be studied. It has also been predicted to be metastable, i.e. it may remain in the metallic state when the pressure is relieved. The metastability of the isotopes shall be studied by reducing the pressure at low temperature, then raising the temperature until the sample converts back to the molecular phase. It may be that hydrogen is not metastable, but deuterium is, due to its smaller zero point energy. Finally, a pressure scale for ultrahigh pressures will be developed. There is no good scale at 500+GPa. A study of the shift of the fluorescence line in nitrogen vacancy nano-diamond can lead to a new pressure calibration scale.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.