Are there published predictions that hydrogen could remain metallic at ambient pressure?

Question

Below the question For the recently reported production (January 2017) of metallic hydrogen in the laboratory - what is the evidence exactly? there is a comment that directed me to the BBC News summary Claim made for hydrogen 'wonder material'.

In their attempt to balance the skepticism of this particular reported observation with the potential implications of producing metallic hydrogen in a laboratory, the BBC included some far-reaching possibilities:

If that is true - and it is a controversial claim - it fulfills a more than 80-year quest to produce what many have said would be a wonder material.

Theory suggests metallic hydrogen could be used to make zero-resistance electrical wiring and super-powerful rocket fuel, among many applications.

At the end of the article:

"The scepticism here is probably a good thing, in that it will drive many groups towards attempting to reproduce this experiment. This publication will certainly incite the field. Again, if it holds up, this is an exciting result. I think in this case time will tell," he told BBC News.

...referring to Marcus Knudson from Sandia National Laboratories.

And Jeffrey McMahon from Washington State University concurred: "With respect to the tiny sample amount: Such experiments are performed in small diamond anvil cells. One challenge would be to make a larger quantity (at once); another, perhaps bigger challenge is to recover even the small sample (ie, remove it from the extreme pressures that it is under in the diamond anvil cell).

"Whether the latter is possible is an important open question."

Question: Are there published, peer-reviewed predictions that hydrogen could remain metallic at ambient pressure? A link or reference would be appreciated. If it's still in pre-print form (AeXiv) that's OK too.

If it's possible, a little help understanding the prediction would be great as well:

I know there are many predicted crystalline forms of water ice at elevated pressures and/or reduced temperatures, and many or most of these have been observed, but I think most of them revert once pressure is reduced to ambient. Also the Tin pest comes to mind. If there is such a prediction of the possibility of hydrogen remaining metallic at ambient, is there an analogous example of this with a material I'm more familliar with, or is this something quite new?

Answer 1

According to http://iopscience.iop.org/article/10.1088/1742-6596/215/1/012194/pdf, "Brovman, Kagan, and Kholas[5] showed that hydrogen would be a metastable metal with a potential barrier of ~1 eV. That is, if the pressure on metallic hydrogen were relaxed, it would remain in the metallic phase, just as diamond is a metastable phase of carbon. However, Salpeter[6] showed that the metastability time of hydrogen might be short due to a tunnelling mechanism in which atoms on the atomic lattice tunnel into molecular states. Since metallic hydrogen is yet to be produced in the laboratory, none of these ideas have been tested." The relevant references are

[5]Brovman EG, Kagan Y, Kholas A. Properties of Metallic Hydrogen under Pressure. Sov Phys JETP. 1972:783-7. [6]Salpeter EE. Evaporation of Cold Metallic Hydrogen. Phys Rev Lett 1972;28(9):560-2.

I did not read the references.

EDIT:(01/28/2017) Reference [5] is at http://www.jetp.ac.ru/cgi-bin/dn/e_034_06_1300.pdf Abstract: "The properties of metallic hydrogen at atmospheric pressure are considered. The problem may be of great theoretical and practical importance. Perturbation theory is employed, which previously was successfully used for analysis of nontransition metals and which takes into account electron-ion interaction up to the third order inclusively. In the given case third-order terms were found to be very essential. It is found that metallic hydrogen tends to crystallize at P=0 into sharply anisotropic structures. This tendency in turn leads to the existence of a whole family of structures with very close energies. All Bravais lattices and the most important two-atom lattices are analyzed. It is found that minimum energy is possessed by a triangular family generated by a primitive hexagonal lattice and yielding a triangular filamentary structure with two-dimensional periodicity. The elastic properties and phonon spectrum of the structure are determined and local stability of the corresponding metastable phase is proven. The properties of metallic hydrogen under pressure will be considered in a separate paper."

Answer 2

A recent NEB calculation based on DFT(see http://aip.scitation.org/doi/10.1063/1.3694793), however, showed that almost all of the currently predicted structures of metallic hydrogen are unstable at zero pressure, and there is no energy barrier between atomic phases and diatomic insulating phases of hydrogen. In addition, the conclusion of Brovman et al was based on simple approximations, and might require further scrutiny.