Electron localization properties in high pressure hydrogen at the liquid-liquid phase transition by Coupled Electron-Ion Monte Carlo

Abstract

We analyze in detail the electronic properties of high pressure hydrogen around the liquid-liquid phase transition based on Coupled Electron-Ion Monte Carlo calculations. Computing the off-diagonal single particle density matrix and the momentum distribution we discuss localization properties of the electrons. The abrupt changes of these distributions indicate a metal to insulator transition occurring together with the structural transition from the atomic to molecular fluid. We further discuss the electron-proton and electron-electron pair correlation functions, which also change abruptly at the transition.

Electronic energy gap closure and metal-insulator transition in dense liquid hydrogen

“…The QMC results for electronic momentum distribution and its Fourier transform, the reduced single particle density matrix along the LLPT have been presented and analysed in Ref. [46]. The asymptotic behavior of the offdiagonal part of the single particle density matrix, n(r), at large distances r discriminates between extended and localized states, the latter decaying faster than r −3 [25].…”

“…FIG. 3:The absolute value of the off-diagonal part of the reduced single particle density matrix, n(r),[46] multiplied by r 3 as a function of distance r for various densities around gap closure. (a) At T = 900, when the gap vanishes for rs < ∼ 1.42, as the liquid crosses the LLPT, the n(r) changes indicating more delocalized, Fermi-liquid like behaviour.…”

Changes in properties of H2 molecules at the fluid–fluid phase transition in warm dense hydrogen

“…The fluid-fluid (or plasma) phase transition in warm dense hydrogen and deuterium is actively studied both experimentally [1][2][3][4][5][6][7][8][9][10][11][12][13] and theoretically, [7,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] but the complete theory has not yet been constructed. Despite being the first and simplest element in the periodic table, hydrogen demonstrates complex behaviour at high pressures and is of significant interest for condensed matter physics at a fundamental level.…”

Molecular Simulation of Covalent Bond Dynamics in Liquid Silicon

“…The covalent bonds in these liquids are dynamic, readily breaking and forming on molecular time scales, and the characterization of these processes is complicated due to the interplay between electronic and nuclear structures. Such metallic liquids include molten silicon, − boron, gallium, and hydrogen at high pressure and temperature, − as well as many alloys, including those of importance in phase change random access memory materials. − These liquids play important roles in fuel cells, catalysis, and electrochemistry, where the dynamic covalent bonds are expected to play an important role in chemical reactivity . Many of these liquids are also found in planetary cores, ,− and understanding their structure and dynamics is of importance to planetary and geophysical sciences.…”