JCP Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

You Tube Flickr Twitter UniPHY Group iResearch App Facebook

Journal of Chemical Physics / Volume 136 / Issue 7 / ARTICLES / Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

J. Chem. Phys. 136, 074504 (2012); http://dx.doi.org/10.1063/1.3679751 (10 pages)

A fresh look at dense hydrogen under pressure. IV. Two structural models on the road from paired to monatomic hydrogen, via a possible non-crystalline phase

Vanessa Labet1, Roald Hoffmann1, and N. W. Ashcroft2

1Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853, USA
2Laboratory of Atomic and Solid State Physics and Cornell Center for Materials Research, Cornell University, Clark Hall, Ithaca, New York 14853, USA

View MapView Map

(Received 19 September 2011; accepted 6 January 2012; published online 15 February 2012)

In this paper, we examine the transition from a molecular to monatomic solid in hydrogen over a wide pressure range. This is achieved by setting up two models in which a single parameter δ allows the evolution from a molecular structure to a monatomic one of high coordination. Both models are based on a cubic Bravais lattice with eight atoms in the unit cell; one belongs to space group Pamath, the other to space group Rmathm. In Pamath one moves from effective 1-coordination, a molecule, to a simple cubic 6-coordinated structure but through a very special point (the golden mean is involved) of 7-coordination. In Rmathm, the evolution is from 1 to 4 and then to 3 to 6-coordinate. If one studies the enthalpy as a function of pressure as these two structures evolve (δ increases), one sees the expected stabilization of minima with increased coordination (moving from 1 to 6 to 7 in the Pamath structure, for instance). Interestingly, at some specific pressures, there are in both structures relatively large regions of phase space where the enthalpy remains roughly the same. Although the structures studied are always higher in enthalpy than the computationally best structures for solid hydrogen – those emerging from the Pickard and Needs or McMahon and Ceperley numerical laboratories – this result is suggestive of the possibility of a microscopically non-crystalline or “soft” phase of hydrogen at elevated pressures, one in which there is a substantial range of roughly equi-enthalpic geometries available to the system. A scaling argument for potential dynamic stabilization of such a phase is presented.

© 2012 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. COMPUTATIONAL DETAILS
  3. PROGRESSIVE EQUALIZATION OF PROTON-PROTON DISTANCES, AND THE PERSISTENCE OF PAIRING: TWO PERIODIC MODELS
    1. Description of the structures
    2. Evolving coordination numbers
    3. At which density might the proton pairs seek to dissociate?
    4. A non-crystalline phase?
    5. A scaling argument
    6. Relative enthalpy of the Pamath and Rmathm structures with respect to other candidates
  4. CONCLUDING COMMENTS
  5. GENERAL CONCLUSION

EDITORIALLY RELATED

    Related Articles

  1. A fresh look at dense hydrogen under pressure. I. An introduction to the problem, and an index probing equalization of H–H distances
    Vanessa Labet et al.
    J. Chem. Phys. 136, 074501 (2012)JCPSA6000136000007074501000001
  2. A fresh look at dense hydrogen under pressure. II. Chemical and physical models aiding our understanding of evolving H–H separations
    Vanessa Labet et al.
    J. Chem. Phys. 136, 074502 (2012)JCPSA6000136000007074502000001
  3. A fresh look at dense hydrogen under pressure. III. Two competing effects and the resulting intra-molecular H-H separation in solid hydrogen under pressure
    Vanessa Labet et al.
    J. Chem. Phys. 136, 074503 (2012)JCPSA6000136000007074503000001

RELATED DATABASES

To view database links for this article, you need to log in.

KEYWORDS and PACS

Keywords

crystal structure, hydrogen, hydrogen bonds, molecular configurations, space groups

PACS

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.3679751

PUBLICATION DATA

ISSN

0021-9606 (print)  
1089-7690 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
    J. Van Kranendonk, Solid Hydrogen (Plenum, New York, 1983).

    V. Labet, R. Hoffmann, and N. W. Ashcroft, J. Chem. Phys. 136, 074503 (2012)JCPSA6000136000007074503000001.

    E. Wigner and H. B. Huntington, J. Chem. Phys. 3, 764 (1935)JCPSA6000003000012000764000001.

    H. K. Mao and R. J. Hemley, Rev. Mod. Phys. 66, 671 (1994).

    J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 78, 1396 (1997).

    J. Felsteiner, Phys. Rev. Lett. 15, 1025 (1965).

    F. London, Phys. Rev. 54, 947 (1938).


Figures (7)

Access to article objects (figures, tables, multimedia) requires a subscription; log in to view available files.
(Access to supplementary files, where available, is free for this journal.)


Close

Google Calendar

ADVERTISEMENT

Your Recent History Recent History Help

Recently Viewed

  1. A fresh look at dense hydrogen under pressure. IV. Two structural models on the road from paired to monatomic hydrogen, via a possible non-crystalline phase
  2. Electronic states and the influence of oxygen addition on the optical absorption behaviour of manganese phthalocyanine
  3. Activation of water on the TiO2 (110) surface: The case of Ti adatoms
  4. Mesoscopic analysis of Gibbs’ criterion for sessile nanodroplets on trapezoidal substrates
  5. The role of surface defects in multi-exciton generation of lead selenide and silicon semiconductor quantum dots
Go to AIP Home
Copyright © American Institute of Physics
close