Lattice stability and high-pressure melting mechanism of dense hydrogen up to 1.5 TPa
Abstract© 2015 American Physical Society. Lattice stability and metastability, as well as melting, are important features of the physics and chemistry of dense hydrogen. Using ab initio molecular dynamics (AIMD), the classical superheating limit and melting line of metallic hydrogen are investigated up to 1.5 TPa. The computations show that the classical superheating degree is about 100 K, and the classical melting curve becomes flat at a level of 350 K when beyond 500 GPa. This information allows us to estimate the well depth and the potential barriers that must be overcome when the crystal melts. Inclusion of nuclear quantum effects (NQE) using path integral molecular dynamics (PIMD) predicts that both superheating limit and melting temperature are lowered to below room temperature, but the latter never reaches absolute zero. Detailed analysis indicates that the melting is thermally activated, rather than driven by pure zero-point motion (ZPM). This argument was further supported by extensive PIMD simulations, demonstrating the stability of Fddd structure against liquefaction at low temperatures.
CitationGeng HY, Hoffmann R, Wu Q (2015) Lattice stability and high-pressure melting mechanism of dense hydrogen up to 1.5 TPa. Physical Review B 92. Available: http://dx.doi.org/10.1103/PhysRevB.92.104103.
SponsorsThis work was supported by the National Natural Science Foundation of China under Grant No.11274281, the CAEP Research Project 2012A0101001, the fund of National Key Laboratory of Shock Wave and Detonation Physics of China (under Grant No. 9140C670105130C67237), the National Science Foundation through Grant No. CHE-0910623, and also by EFree, an Energy Frontier Research Center funded by the US Department of Energy (Award No. DESC0001057 at Cornell). Computation was performed using the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. OCI-1053575, the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECCS-0335765), and the resources of the Supercomputing Laboratory at King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia.
PublisherAmerican Physical Society (APS)
JournalPhysical Review B