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Title: Electronic structure and electron-phonon coupling in TiH$$_2$$

Abstract

Calculations using first principles methods and strong coupling theory are carried out to understand the electronic structure and superconductivity in cubic and tetragonal TiH$$_2$$. A large electronic density of states at the Fermi level in the cubic phase arises from Ti-$$t_{2g}$$ states and leads to a structural instability against tetragonal distortion at low temperatures. However, constraining the in-plane lattice constants diminishes the energy gain associated with the tetragonal distortion, allowing the cubic phase to be stable at low temperatures. Furthermore, calculated phonon dispersions show decoupled acoustic and optic modes arising from Ti and H vibrations, respectively and frequencies of optic modes to be rather high. The cubic phase has a large electron-phonon coupling parameter $$\lambda$$ and critical temperature of several K. Contribution of the hydrogen sublattice to $$\lambda$$ is found to be small in this material, which we understand from strong coupling theory to be due to the small H-$s$ DOS at the Fermi level and high energy of hydrogen modes at the tetrahedral sites.

Authors:
 [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1266003
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
electronic structure; superconducting properties and materials

Citation Formats

Shanavas, Kavungal Veedu, Lindsay, Lucas R., and Parker, David S. Electronic structure and electron-phonon coupling in TiH$_2$. United States: N. p., 2016. Web. doi:10.1038/srep28102.
Shanavas, Kavungal Veedu, Lindsay, Lucas R., & Parker, David S. Electronic structure and electron-phonon coupling in TiH$_2$. United States. doi:10.1038/srep28102.
Shanavas, Kavungal Veedu, Lindsay, Lucas R., and Parker, David S. Wed . "Electronic structure and electron-phonon coupling in TiH$_2$". United States. doi:10.1038/srep28102. https://www.osti.gov/servlets/purl/1266003.
@article{osti_1266003,
title = {Electronic structure and electron-phonon coupling in TiH$_2$},
author = {Shanavas, Kavungal Veedu and Lindsay, Lucas R. and Parker, David S.},
abstractNote = {Calculations using first principles methods and strong coupling theory are carried out to understand the electronic structure and superconductivity in cubic and tetragonal TiH$_2$. A large electronic density of states at the Fermi level in the cubic phase arises from Ti-$t_{2g}$ states and leads to a structural instability against tetragonal distortion at low temperatures. However, constraining the in-plane lattice constants diminishes the energy gain associated with the tetragonal distortion, allowing the cubic phase to be stable at low temperatures. Furthermore, calculated phonon dispersions show decoupled acoustic and optic modes arising from Ti and H vibrations, respectively and frequencies of optic modes to be rather high. The cubic phase has a large electron-phonon coupling parameter $\lambda$ and critical temperature of several K. Contribution of the hydrogen sublattice to $\lambda$ is found to be small in this material, which we understand from strong coupling theory to be due to the small H-$s$ DOS at the Fermi level and high energy of hydrogen modes at the tetrahedral sites.},
doi = {10.1038/srep28102},
journal = {Scientific Reports},
number = ,
volume = 6,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}

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