skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures

Abstract

The authors have conducted Ab initio molecular dynamics simulations of hydrogen fluoride (HF) at pressures of 5-66 GPa along the 900 K isotherm. They predict a superionic phase at 33 GPa, where the fluorine atoms are fixed in a bcc lattice while the hydrogen atoms diffuse rapidly with a diffusion constant of between 2 x 10{sup -5} and 5 x 10{sup -5} cm{sup 2}/s. They find that a transformation from asymmetric to symmetric hydrogen bonding occurs in HF at 66 GPa and 900 K. With superionic HF they have discovered a model system where symmetric hydrogen bonding occurs at experimentally achievable conditions. Given previous results on superionic H{sub 2}O[1,2,3] and NH{sub 3}[1], they conclude that high P,T superionic phases of electronegative element hydrides could be common.

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
897967
Report Number(s):
UCRL-JRNL-220577
TRN: US200706%%159
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics, vol. 125, no. 4, July 24, 2006, pp. 044501
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 58 GEOSCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMS; BCC LATTICES; BONDING; DIFFUSION; FLUORINE; HYDRIDES; HYDROFLUORIC ACID; HYDROGEN; ISOTHERMS; SIMULATION; TRANSFORMATIONS

Citation Formats

Goldman, N, and Fried, L E. First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures. United States: N. p., 2006. Web. doi:10.1063/1.2220036.
Goldman, N, & Fried, L E. First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures. United States. doi:10.1063/1.2220036.
Goldman, N, and Fried, L E. Mon . "First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures". United States. doi:10.1063/1.2220036. https://www.osti.gov/servlets/purl/897967.
@article{osti_897967,
title = {First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures},
author = {Goldman, N and Fried, L E},
abstractNote = {The authors have conducted Ab initio molecular dynamics simulations of hydrogen fluoride (HF) at pressures of 5-66 GPa along the 900 K isotherm. They predict a superionic phase at 33 GPa, where the fluorine atoms are fixed in a bcc lattice while the hydrogen atoms diffuse rapidly with a diffusion constant of between 2 x 10{sup -5} and 5 x 10{sup -5} cm{sup 2}/s. They find that a transformation from asymmetric to symmetric hydrogen bonding occurs in HF at 66 GPa and 900 K. With superionic HF they have discovered a model system where symmetric hydrogen bonding occurs at experimentally achievable conditions. Given previous results on superionic H{sub 2}O[1,2,3] and NH{sub 3}[1], they conclude that high P,T superionic phases of electronegative element hydrides could be common.},
doi = {10.1063/1.2220036},
journal = {Journal of Chemical Physics, vol. 125, no. 4, July 24, 2006, pp. 044501},
number = ,
volume = ,
place = {United States},
year = {Mon Apr 10 00:00:00 EDT 2006},
month = {Mon Apr 10 00:00:00 EDT 2006}
}
  • The aggregation of superheated hydrogen fluoride vapor is explored through the use of Monte Carlo simulations employing Kohn-Sham density functional theory with the exchange/correlation functional of Becke-Lee-Yang-Parr to describe the molecular interactions. Simulations were carried out in the canonical ensemble for a system consisting of ten molecules at constant density (2700 Å 3/molecule) and at three different temperatures (T = 310, 350, and 390 K). Aggregation-volume-bias and configurational-bias Monte Carlo approaches (along with pre-sampling with an approximate potential) were employed to increase the sampling efficiency of cluster formation and destruction.
  • The phase stability of Nb 90Zr 10 alloy at high temperatures and compression is explored by means of first-principles electronic-structure calculations. Utilizing the self-consistent ab initio lattice dynamics (SCAILD) approach in conjunction with density-functional theory, we show that pressure-induced mechanical instability of the body-centered cubic phase, which results in formation of a rhombohedral phase at around 50 GPa, will prevail significant heating. As a result, the body-centered cubic structure will recover before melting at ~1800 K.
  • In this paper, two binary phases in the system Hf-O have been synthesized at pressures between 12 and 34 GPa and at temperatures up to 3000 K by reacting Hf with HfO 2 using a laser-heated diamond anvil cell. In situ X-ray diffraction in conjunction with density functional theory calculations has been employed to characterize a previously unreported tetragonal Hf 8O 7 phase. This phase has a structure which is based on an fcc Hf packing with oxygen atoms occupying octahedral interstitial positions. Its predicted bulk modulus is 223(1) GPa. The second phase has a composition close to Hf 6O,more » where oxygen atoms occupy octahedral interstitial sites in an hcp Hf packing. Its experimentally determined bulk modulus is 128(30) GPa. Finally, the phase diagram of Hf metal was further constrained at high pressures and temperatures, where we show that α-Hf transforms to β-Hf around 2160(150) K and 18.2 GPa and β-Hf remains stable up to at least 2800 K at this pressure.« less
  • Quasiparticle calculations have been performed for the band gap of solid molecular hydrogen in the hcp structure. The calculations predict that the orientationally ordered phase undergoes metallization due to an indirect band overlap at the volume {ital V}=2.50 cm{sup 3}/mol and the orientationally disordered phase at {ital V}=1.89 cm{sup 3}/mol, which correspond to metallization pressures of 151 and 300 GPa, respectively. A quantitative relation between the degree of orientational order and the metallization volume is obtained.