Title: Evaluation of exchange-correlation functionals with multiple-shock conductivity measurements in hydrogen and deuterium at the molecular-to-atomic transition

Abstract

The temperature (T) and density (ρ) conditions at which hydrogen undergoes a molecular-to-atomic (MA) transition is crucial to our understanding of the gas-giant planets such as Jupiter and Saturn. First-principles (FP) calculations suggest that this transition is coincident with metallization and acts as a catalyst for hydrogen-helium demixing, which has significant consequences for models of planetary interiors. Prediction of this transition boundary has proven to be difficult using FP methods. In particular, detailed comparisons of finite temperature density functional theory (FT-DFT) calculations of the MA transition in both the high-T, low-ρ regime, where the transition is largely T driven, and the low-T, high-ρ regime, where the transition is largely ρ driven, suggest that the transition is very sensitive to the exchange-correlation (xc) functional used in the calculation. Here we present a detailed comparison of previous multiple-shock electrical conductivity measurements with FT-DFT calculations employing various xc functionals to probe a regime where both T and ρ play an important role in the transition. The measurement results are found to be inconsistent with the semilocal xc functional PBE and are in much better agreement with the nonlocal xc functionals vdW-DF1 and vdW-DF2. Furthermore, we show that the inconsistency with PBE likely stemsmore » from pressure errors associated with the PBE xc functional, resulting in calculated pressures that are too low at these T and ρ conditions. Together with previous comparisons at high-T, low-ρ and low-T, high-ρ these results provide a consistent picture for the MA transition over a wide T and ρ range. Here, this picture may also provide insight into differences in experimental observations of the metallization of liquid hydrogen and deuterium in the low-T regime.« less

Authors:

Knudson, M. D. ^[1]; Desjarlais, M. P. ^[2]; Preising, M. ^[3]; Redmer, R. ^[3]

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+ Show Author Affiliations

1. Washington State Univ., Pullman, WA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Univ. of Rostock, Rostock (Germany)

Publication Date:

2018-11-26

Research Org.:

Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)

OSTI Identifier:

1493764

Alternate Identifier(s):

OSTI ID: 1492145

Grant/Contract Number:  

NA0002007; NA0003525

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 98; Journal Issue: 17; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 08 HYDROGEN