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Title: Kohn Anomaly and Phase Stability in Group VB Transition Metals

In the periodic table, only a few pure metals exhibit lattice or magnetic instabilities associated with Fermi surface nesting, the classical examples being α-U and Cr. Whereas α-U displays a strong Kohn anomaly in the phonon spectrum that ultimately leads to the formation of charge density waves (CDWs), Cr is known for its nesting-induced spin density waves (SDWs). Recently, it has become clear that a pronounced Kohn anomaly and the corresponding softening in the elastic constants is also the key factor that controls structural transformations and mechanical properties in compressed group VB metals—materials with relatively high superconducting critical temperatures. This article reviews the current understanding of the structural and mechanical behavior of these metals under pressure with an introduction to the concept of the Kohn anomaly and how it is related to the important concept of Peierls instability. We review both experimental and theoretical results showing different manifestations of the Kohn anomaly in the transverse acoustic phonon mode TA (ξ00) in V, Nb, and Ta. Specifically, in V the anomaly triggers a structural transition to a rhombohedral phase, whereas in Nb and Ta it leads to an anomalous reduction in yield strength.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physics Division
  2. Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Lab.
  3. KTH Royal Inst. of Technology, Stockholm (Sweden). Dept. of Materials Science and Engineering; Wigner Research Center for Physics, Inst. for Solid State Physics and Optics, Budapest (Hungary); Uppsala Univ. (Sweden). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
LLNL-JRNL-746745
Journal ID: ISSN 2079-3197
Grant/Contract Number:
AC52-07NA27344; NA0002006; SC0001057
Type:
Accepted Manuscript
Journal Name:
Computation
Additional Journal Information:
Journal Volume: 6; Journal Issue: 2; Journal ID: ISSN 2079-3197
Publisher:
MDPI
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Energy Frontier Research Centers (EFRC) (United States). Energy Frontier Research in Extreme Environments (EFree)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Swedish Research Council (SRC); Swedish Foundation for Strategic Research; Hungarian Scientific Research Fund (OTKA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Kohn anomaly; Fermi surface nesting; phonon softening
OSTI Identifier:
1438810

Landa, Alexander, Soderlind, Per, Naumov, Ivan, Klepeis, John, and Vitos, Levente. Kohn Anomaly and Phase Stability in Group VB Transition Metals. United States: N. p., Web. doi:10.3390/computation6020029.
Landa, Alexander, Soderlind, Per, Naumov, Ivan, Klepeis, John, & Vitos, Levente. Kohn Anomaly and Phase Stability in Group VB Transition Metals. United States. doi:10.3390/computation6020029.
Landa, Alexander, Soderlind, Per, Naumov, Ivan, Klepeis, John, and Vitos, Levente. 2018. "Kohn Anomaly and Phase Stability in Group VB Transition Metals". United States. doi:10.3390/computation6020029. https://www.osti.gov/servlets/purl/1438810.
@article{osti_1438810,
title = {Kohn Anomaly and Phase Stability in Group VB Transition Metals},
author = {Landa, Alexander and Soderlind, Per and Naumov, Ivan and Klepeis, John and Vitos, Levente},
abstractNote = {In the periodic table, only a few pure metals exhibit lattice or magnetic instabilities associated with Fermi surface nesting, the classical examples being α-U and Cr. Whereas α-U displays a strong Kohn anomaly in the phonon spectrum that ultimately leads to the formation of charge density waves (CDWs), Cr is known for its nesting-induced spin density waves (SDWs). Recently, it has become clear that a pronounced Kohn anomaly and the corresponding softening in the elastic constants is also the key factor that controls structural transformations and mechanical properties in compressed group VB metals—materials with relatively high superconducting critical temperatures. This article reviews the current understanding of the structural and mechanical behavior of these metals under pressure with an introduction to the concept of the Kohn anomaly and how it is related to the important concept of Peierls instability. We review both experimental and theoretical results showing different manifestations of the Kohn anomaly in the transverse acoustic phonon mode TA (ξ00) in V, Nb, and Ta. Specifically, in V the anomaly triggers a structural transition to a rhombohedral phase, whereas in Nb and Ta it leads to an anomalous reduction in yield strength.},
doi = {10.3390/computation6020029},
journal = {Computation},
number = 2,
volume = 6,
place = {United States},
year = {2018},
month = {3}
}