Edwards B, Ashcroft N W
Department of Radiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Proc Natl Acad Sci U S A. 2004 Mar 23;101(12):4013-8. doi: 10.1073/pnas.0307331101. Epub 2004 Mar 17.
By increase in density, impelled by pressure, the electronic energy bands in dense hydrogen attain significant widths. Nevertheless, arguments can be advanced suggesting that a physically consistent description of the general consequences of this electronic structure can still be constructed from interacting but state-dependent multipoles. These reflect, in fact self-consistently, a disorder-induced localization of electron states partially manifesting the effects of proton dynamics; they retain very considerable spatial inhomogeneity (as they certainly do in the molecular limit). This description, which is valid provided that an overall energy gap has not closed, leads at a mean-field level to the expected quadrupolar coupling, but also for certain structures to the eventual emergence of dipolar terms and their coupling when a state of broken charge symmetry is developed. A simple Hamiltonian incorporating these basic features then leads to a high-density, low-temperature phase diagram that appears to be in substantial agreement with experiment. In particular, it accounts for the fact that whereas the phase I-II phase boundary has a significant isotope dependence, the phase II-III boundary has very little.
在压力作用下，通过密度增加，致密氢中的电子能带达到显著宽度。然而，可以提出这样的观点，即仍然可以从相互作用但依赖于状态的多极子构建对这种电子结构一般后果的物理上一致的描述。事实上，这些多极子自洽地反映了无序诱导的电子态局域化，部分体现了质子动力学的影响；它们保留了非常显著的空间不均匀性（就像在分子极限情况下肯定会有的那样）。只要整体能隙没有关闭，这种描述就是有效的，在平均场水平上会导致预期的四极耦合，但对于某些结构，当电荷对称性破缺状态发展时，也会导致偶极项及其耦合的最终出现。包含这些基本特征的一个简单哈密顿量进而导致一个高密度、低温相图，该相图似乎与实验结果基本一致。特别是，它解释了这样一个事实，即虽然I-II相边界有显著的同位素依赖性，但II-III相边界的依赖性很小。
