The solid hydrogen compounds D2, HD and H2 remain quantum molecular solids up to pressures in the 100 GPa range1. A remarkable macroscopic consequence is the existence of a pressure-induced broken symmetry phase transition2,3,4, in which the molecules go from a spherical rotational state to an anisotropic rotational state. Theoretical understanding of the broken symmetry phase structure remains controversial, despite numerous studies5,6,7,8,9,10. Some open questions concern the existence of long- or short-range orientational order; whether a strong isotopic shift on the transition pressure should be assigned to the nuclear zero-point motion or to quantum localization; and whether the structures are cubic, hexagonal or orthorhombic. Here we present experimental data on the structure of the broken symmetry phase in solid D2, obtained by a combination of neutron and X-ray diffraction up to 60 GPa. Our data are incompatible with orthorhombic structures predicted by recent theoretical works. We find that the broken symmetry phase structure is incommensurate with local orientational order, being similar to that found in metastable cubic para-D2.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Mazin, I., Hemley, R., Goncharov, A., Hanfland, M. & Mao, H. K. Quantum and classical orientational ordering in solid hydrogen. Phys. Rev. Lett. 78, 1066–1069 (1997)
Silvera, I. F. & Wijngaarden, R. J. New low-temperature phase of molecular deuterium at ultrahigh pressure. Phys. Rev. Lett. 47, 39–42 (1981)
Lorenzana, H. E., Silvera, I. F. & Goettel, K. A. Evidence for a structural phase transition in solid hydrogen at megabar pressures. Phys. Rev. Lett. 63, 2080–2083 (1989)
Moshary, F., Chen, N. & Silvera, I. Remarkable high pressure phase line and orientational order in solid hydrogen deuteride. Phys. Rev. Lett. 71, 3814–3817 (1993)
Cui, T., Cheng, E., Alder, B. J. & Whaley, K. B. Rotational ordering in solid deuterium and hydrogen: A path integral Monte Carlo study. Phys. Rev. B 55, 12253–12266 (1997)
Kitamura, H., Tsuneyuki, Sh., Tadashi, O. & Miyake, T. Quantum distribution of protons in solid molecular hydrogen at megabar pressures. Nature 404, 259–262 (2000)
Kohanoff, J., Scandalo, S., Chiarotti, G. L. & Tosatti, E. Solid molecular hydrogen: The broken symmetry phase. Phys. Rev. Lett. 78, 2783–2786 (1997)
Johnson, K. A. & Ashcroft, N. W. Structure and bandgap closure in dense hydrogen. Nature 403, 632–635 (2000)
Stadele, M. & Martin, R. Metallization of molecular hydrogen: prediction from exact-exchange calculations. Phys. Rev. Lett. 84, 6070–6073 (2000)
Nagao, K., Takezawa, T. & Nagara, H. Ab initio calculation of optical-mode frequencies in compressed solid hydrogen. Phys. Rev. B 59, 13741–13753 (1999)
Van Kranendonk, J. Solid hydrogen: theory of the properties of solid H2, HD, D2 (Plenum, New York, 1983)
Kaxiras, E. & Guo, Z. Orientational order in dense molecular hydrogen: A first-principles path-integral Monte Carlo calculation. Phys. Rev. B 49, 11822–11832 (1994)
Raich, J. & Etters, R. Rotational molecular motion in solid H2 and D2 under pressure. J. Low Temp. Phys. 6, 229–240 (1972)
Goncharov, A. F., Eggert, J. H., Mazin, I. I., Hemley, R. J. & Mao, H. K. Raman excitations and orientational ordering in deuterium at high pressure. Phys. Rev. B 54, R15590–R15593 (1996)
Freiman, Y., Tretyak, S., Antsygina, T. & Hemley, R. Novel phase behavior in quantum rotors. J. Low Temp. Phys. 133, 251–260 (2003)
Loubeyre, P. et al. X-ray diffraction and equation of state of hydrogen at megabar pressures. Nature 383, 702–704 (1996)
Goncharenko, I. N. Neutron diffraction experiments in diamond and sapphire pressure cells. High Press. Res. 24, 193–204 (2004)
Cui, L., Chen, H., Leon, S. & Silvera, I. Megabar pressure triple point in solid deuterium. Phys. Rev. Lett. 72, 3048–3051 (1994)
Miyagi, H. & Nakamura, T. Ground state energy difference of hcp and fcc ortho-hydrogens. Prog. Theor. Phys. 37, 641–660 (1967)
James, H. Orientational order in solid ortho-hydrogen. Hexagonal close-packed molecular lattice. Phys. Rev. 167, 862–874 (1968)
Hetényi, B., Scandolo, S. & Tosatti, E. Theoretical evidence for a reentrant phase diagram in ortho-para mixtures of solid H2 at high pressure. Phys. Rev. Lett. 94, 125503 (2005)
Goncharov, A., Hemley, R., Mao, H. K. & Shu, J. New high-pressure excitations in parahydrogen. Phys. Rev. Lett. 80, 101–104 (1998)
Pravica, M. & Silvera, I. F. NMR study of ortho-para conversion at high pressure in hydrogen. Phys. Rev. Lett. 81, 4180–4183 (1998)
Eggert, J., Karmon, E., Hemley, R., Mao, H. K. & Goncharov, A. Pressure-enhanced ortho-para conversion in solid hydrogen up to 58 GPa. Proc. Natl Acad. Sci. USA 96, 12269–12272 (1999)
We thank A. Goukasov and O. Makarova for help in neutron experiments, and R. LeToullec, F. Occelli, M. Hanfland and M. Mezouar for help with the X-ray work.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
About this article
International Reviews in Physical Chemistry (2019)
High Pressure Research (2019)
The Journal of Chemical Physics (2019)
Nuclear Magnetic Resonance Spectroscopy as a Dynamical Structural Probe of Hydrogen under High Pressure
Physical Review Letters (2019)
Journal of Applied Crystallography (2018)