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

Title: Polymorphism and melt in high-pressure tantalum. II. Orthorhombic phases

Abstract

Continuing uncertainty in the high-pressure melt curves of bcc transition metals has spawned renewed research interest in the phase diagrams of these materials, with tantalum becoming an important prototype. Here, the present paper extends the quantum-based investigation of high- T, P polymorphism and melt in Ta that was begun in Paper I [Haskins et al., Phys. Rev. B 86, 224104 (2012)] on five candidate cubic and hexagonal structures (bcc, A15, fcc, hcp, and hex-ω) to here treat four promising orthorhombic structures (Pnma, Fddd, Pmma, and α-U). Using DFT-based MGPT multi-ion potentials that allow accurate MD simulations of large systems, we showed in Paper I that the mechanically unstable fcc, hcp, and hex-ω structures can only be stabilized at high- T , P by large anharmonic vibrational effects, requiring systems of ~500 atoms to produce size-independent melt curves and reliable calculations of thermodynamic stability. This reversed a previous small-cell quantum-simulation prediction of a high- T , P hex-ω phase. Subsequent DFT calculations have now suggested a more energetically favorable and mechanically stable Pnma structure, which again small-cell quantum simulations predict could be a high- T , P phase. Our present MGPT total-energy and phonon calculations show that not only Pnma, butmore » all four orthorhombic structures considered here, are similarly energetically favorable, and that Fddd in addition to Pnma is mechanically stable at T = 0 up to 420 GPa. MGPT-MD simulations further reveal spontaneous temperature-induced Pnma → bcc and Fddd → bcc transformations at modest temperatures, peaking at ~1450 K near 100 GPa. At high temperatures near melt, we find T -dependent c / a and b / a axial ratios and large stabilizing anharmonicity present in all four orthorhombic structures. The anharmonicity drives significantly larger melt size effects, requiring systems of ~1000 – 4000 atoms to produce converged melt curves for reliable predictions of relative thermodynamic stability. In the large-cell limit, with ~40000 solid-phase atoms and accurate two-phase MGPT-MD melt simulation, we find that Pnma, Fddd and α-U have melt temperatures that are equal to bcc over small pressure ranges in the vicinity of 100 GPa, but that the orthorhombic melt temperatures never exceed bcc up to 420 GPa. This finding suggests that Pnma, Fddd, and α-U remain highly competitive metastable phases that could coexist with bcc and possibly be observed experimentally. Finally, to add additional insight into our results we have constructed global Helmholtz free energies for the A15, Pnma, and Fddd phases of Ta, complementing previous free energies obtained for the bcc, fcc, and liquid phases.« less

Authors:
 [1];  [2]
  1. NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States). AMA, Inc.
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1488793
Alternate Identifier(s):
OSTI ID: 1477532
Report Number(s):
LLNL-JRNL-742878
Journal ID: ISSN 2469-9950; PRBMDO; 897103
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 98; Journal Issue: 14; 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

Citation Formats

Haskins, Justin B., and Moriarty, John A. Polymorphism and melt in high-pressure tantalum. II. Orthorhombic phases. United States: N. p., 2018. Web. doi:10.1103/PhysRevB.98.144107.
Haskins, Justin B., & Moriarty, John A. Polymorphism and melt in high-pressure tantalum. II. Orthorhombic phases. United States. doi:10.1103/PhysRevB.98.144107.
Haskins, Justin B., and Moriarty, John A. Thu . "Polymorphism and melt in high-pressure tantalum. II. Orthorhombic phases". United States. doi:10.1103/PhysRevB.98.144107. https://www.osti.gov/servlets/purl/1488793.
@article{osti_1488793,
title = {Polymorphism and melt in high-pressure tantalum. II. Orthorhombic phases},
author = {Haskins, Justin B. and Moriarty, John A.},
abstractNote = {Continuing uncertainty in the high-pressure melt curves of bcc transition metals has spawned renewed research interest in the phase diagrams of these materials, with tantalum becoming an important prototype. Here, the present paper extends the quantum-based investigation of high- T, P polymorphism and melt in Ta that was begun in Paper I [Haskins et al., Phys. Rev. B 86, 224104 (2012)] on five candidate cubic and hexagonal structures (bcc, A15, fcc, hcp, and hex-ω) to here treat four promising orthorhombic structures (Pnma, Fddd, Pmma, and α-U). Using DFT-based MGPT multi-ion potentials that allow accurate MD simulations of large systems, we showed in Paper I that the mechanically unstable fcc, hcp, and hex-ω structures can only be stabilized at high- T , P by large anharmonic vibrational effects, requiring systems of ~500 atoms to produce size-independent melt curves and reliable calculations of thermodynamic stability. This reversed a previous small-cell quantum-simulation prediction of a high- T , P hex-ω phase. Subsequent DFT calculations have now suggested a more energetically favorable and mechanically stable Pnma structure, which again small-cell quantum simulations predict could be a high- T , P phase. Our present MGPT total-energy and phonon calculations show that not only Pnma, but all four orthorhombic structures considered here, are similarly energetically favorable, and that Fddd in addition to Pnma is mechanically stable at T = 0 up to 420 GPa. MGPT-MD simulations further reveal spontaneous temperature-induced Pnma → bcc and Fddd → bcc transformations at modest temperatures, peaking at ~1450 K near 100 GPa. At high temperatures near melt, we find T -dependent c / a and b / a axial ratios and large stabilizing anharmonicity present in all four orthorhombic structures. The anharmonicity drives significantly larger melt size effects, requiring systems of ~1000 – 4000 atoms to produce converged melt curves for reliable predictions of relative thermodynamic stability. In the large-cell limit, with ~40000 solid-phase atoms and accurate two-phase MGPT-MD melt simulation, we find that Pnma, Fddd and α-U have melt temperatures that are equal to bcc over small pressure ranges in the vicinity of 100 GPa, but that the orthorhombic melt temperatures never exceed bcc up to 420 GPa. This finding suggests that Pnma, Fddd, and α-U remain highly competitive metastable phases that could coexist with bcc and possibly be observed experimentally. Finally, to add additional insight into our results we have constructed global Helmholtz free energies for the A15, Pnma, and Fddd phases of Ta, complementing previous free energies obtained for the bcc, fcc, and liquid phases.},
doi = {10.1103/PhysRevB.98.144107},
journal = {Physical Review B},
number = 14,
volume = 98,
place = {United States},
year = {2018},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

FIG. 1 FIG. 1: High-pressure bcc melting in Ta, as obtained from MGPT free energies, QMD simulations, and DFT-TPT calculations, and compared with experimental data from both historical and new [DAC measurements (solid circles with error bars and solid diamonds), and with data from isobaric and shock measurements.

Save / Share:

Works referenced in this record:

Molybdenum at High Pressure and Temperature: Melting from Another Solid Phase
journal, April 2008


Shock-Induced Omega Phase in Tantalum
journal, April 1998


Z methodology for phase diagram studies: platinum and tantalum as examples
journal, May 2014


High-pressure, high-temperature thermophysical measurements on tantalum and tungsten
journal, January 1986

  • Berthault, A.; Arles, L.; Matricon, J.
  • International Journal of Thermophysics, Vol. 7, Issue 1
  • DOI: 10.1007/BF00503808

Acoustic Velocities and Phase Transitions in Molybdenum under Strong Shock Compression
journal, February 1989


Melting of tantalum at high pressure determined by angle dispersive x-ray diffraction in a double-sided laser-heated diamond-anvil cell
journal, October 2003

  • Errandonea, D.; Somayazulu, M.; Häusermann, D.
  • Journal of Physics: Condensed Matter, Vol. 15, Issue 45
  • DOI: 10.1088/0953-8984/15/45/003

Simulating solidification in metals at high pressure: The drive to petascale computing
journal, September 2006

  • Streitz, Frederick H.; Glosli, James N.; Patel, Mehul V.
  • Journal of Physics: Conference Series, Vol. 46
  • DOI: 10.1088/1742-6596/46/1/037

Ab initio based empirical potential used to study the mechanical properties of molybdenum
journal, June 2012


Shock-induced deformation twinning and omega transformation in tantalum and tantalum–tungsten alloys
journal, December 2000


Angular forces and melting in bcc transition metals: A case study of molybdenum
journal, May 1994


Efficient wide-range calculation of free energies in solids and liquids using reversible-scaling molecular dynamics
journal, August 2014


Analytic representation of multi-ion interatomic potentials in transition metals
journal, July 1990


Quantum-based atomistic simulation of materials properties in transition metals
journal, March 2002

  • Moriarty, John A.; Belak, James F.; Rudd, Robert E.
  • Journal of Physics: Condensed Matter, Vol. 14, Issue 11
  • DOI: 10.1088/0953-8984/14/11/305

High Melting Points of Tantalum in a Laser-Heated Diamond Anvil Cell
journal, June 2010


Fast Parallel Algorithms for Short-Range Molecular Dynamics
journal, March 1995


X-ray diffraction measurements of Mo melting to 119 GPa and the high pressure phase diagram
journal, March 2009

  • Santamaría-Pérez, D.; Ross, M.; Errandonea, D.
  • The Journal of Chemical Physics, Vol. 130, Issue 12
  • DOI: 10.1063/1.3082030

Melting line of aluminum from simulations of coexisting phases
journal, February 1994


Predicted alternative structure for tantalum metal under high pressure and high temperature
journal, August 2013

  • Liu, Zhong-Li; Cai, Ling-Cang; Zhang, Xiu-Lu
  • Journal of Applied Physics, Vol. 114, Issue 7
  • DOI: 10.1063/1.4818963

High-Pressure—High-Temperature Polymorphism in Ta: Resolving an Ongoing Experimental Controversy
journal, June 2010


Quantum-Mechanical Interatomic Potentials with Electron Temperature for Strong-Coupling Transition Metals
journal, January 2012


Phase Transformation in Tantalum under Extreme Laser Deformation
journal, October 2015

  • Lu, C. -H.; Hahn, E. N.; Remington, B. A.
  • Scientific Reports, Vol. 5, Issue 1
  • DOI: 10.1038/srep15064

Pressure Induces Major Changes in the Nature of Americium's 5 f Electrons
journal, October 2000


Melting curve of tantalum from first principles
journal, June 2007


Shock-induced displacive transformations in tantalum and tantalum-tungsten alloys
journal, August 1998


Hugoniot temperatures and melting of tantalum under shock compression determined by optical pyrometry
journal, August 2009

  • Dai, Chengda; Hu, Jianbo; Tan, Hua
  • Journal of Applied Physics, Vol. 106, Issue 4
  • DOI: 10.1063/1.3204941

Robust quantum-based interatomic potentials for multiscale modeling in transition metals
journal, March 2006

  • Moriarty, John A.; Benedict, Lorin X.; Glosli, James N.
  • Journal of Materials Research, Vol. 21, Issue 3
  • DOI: 10.1557/jmr.2006.0070

Ca-VI: A high-pressure phase of calcium above 158 GPa
journal, April 2010


Quantum molecular dynamics simulations of uranium at high pressure and temperature
journal, July 2008


Flash melting of tantalum in a diamond cell to 85 GPa
journal, February 2016


Shock-induced phase transformation in tantalum
journal, September 2010


Systematics of transition-metal melting
journal, March 2001


Thermal Properties of the Inhomogeneous Electron Gas
journal, March 1965


Melting curve of face-centered-cubic nickel from first-principles calculations
journal, July 2013


First-Principles Simulations of Lithium Melting: Stability of the bcc Phase Close to Melting
journal, May 2010


First-principles theory of Ta up to 10 Mbar pressure: Structural and mechanical properties
journal, May 1998


Stable structures of tantalum at high temperature and high pressure
journal, August 2013


Sound velocity variations and melting of vanadium under shock compression
journal, October 2001

  • Dai, Chengda; Jin, Xiaogang; Zhou, Xianming
  • Journal of Physics D: Applied Physics, Vol. 34, Issue 20
  • DOI: 10.1088/0022-3727/34/20/310

Melting and critical superheating
journal, January 2006


Self-Consistent Equations Including Exchange and Correlation Effects
journal, November 1965


Melting temperature of tungsten from two ab initio approaches
journal, September 2011


Thermophysical properties of solid and liquid tungsten
journal, July 1990

  • Hixson, R. S.; Winkler, M. A.
  • International Journal of Thermophysics, Vol. 11, Issue 4
  • DOI: 10.1007/BF01184339

Polymorphism and melt in high-pressure tantalum
journal, December 2012


Evidences of transitory metastable phases in refractory metals solidified from highly undercooled liquids in a drop tube
journal, March 1993