Metallic Properties of the Isotopes of Hydrogen

氢原子由一个质子和一个结合在一起的单电子组成。氢核是由质子和中子组成的，所以它的质量是氢的两倍。这项研究的目的是研究氢同位素的性质：氢、氢和金属相(氚被省略，因为它是放射性的)，统称为氢。一般来说，元素的同位素效应很小，大约在百分之一或两个百分点左右。在氢气中，D2与H2的质量比为200%，对行为的影响可能非常大。例如，氢的一个重要的量子方面是凝聚态中的零点能量或运动。其结果是，在零温度极限下，原子或分子不在晶格位置上的固定位置，而是在这些位置周围运动。这种材料的凝固温度非常低(分子氢，约14K；氢约18K)。氦甚至比分子氢更量子，而且没有固态，在T=0K时保持液态。氢原子本身被预测为液态基态。研究小组计划研究高压对氢气的影响。该研究小组已经在实验中证明，作为一种稳定的分子，氢化氢在约200 Gpa的压力下变得不稳定，解离并重新结合形成稳定的HD、D2和H2的混合物。因此，在这项研究中，应该研究同位素在超高压和低温下的性质。技术摘要研究的计划是研究氢在压力下的性质，这些氢是金属的。在研究计划中，已经表明氢在~500 Gpa时成为一种金属。由于分子氢的质量较大，其零点能量较小，结合能较大，因此预计氢的压强会较高。高清应该会有很多惊喜，因为在~200 GPA以上，它变成了0.5高清和0.25(H2+D2)的混合体。可能需要500 Gpa的压力才能解离H2分子，但在更低的压力下，HD可能会变得不稳定。这项研究预计会有惊喜。一旦同位素金属化，将通过X射线分析来研究基态。关于氢的一个有趣的预测是，它可能是一个室温超导体，这一点将被研究。它也被预测为亚稳态，即当压力释放时，它可能保持在金属状态。通过在低温下降低压力，然后升高温度，直到样品转变回分子相，来研究同位素的亚稳性。氢可能不是亚稳态的，但由于其零点能量较小，氢是亚稳态的。最后，将开发出适用于超高压的压力表。在GPA超过500的情况下，没有好的规模。对氮空位纳米钻石中荧光线移动的研究可以产生一个新的压力校准标尺。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.