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Title: First-principles study of crystalline and amorphous AlMgB 14-based materials

Abstract

Here, we report first-principles investigations of crystalline and amorphous boron and M1 xM2 yX zB 14-z (M1, M2 = Al, Mg, Li, Na, Y; X = Ti, C, Si) phases (so-called “BAM” materials). Phase stability is analyzed in terms of formation energy and dynamical stability. The atomic configurations as well as the electronic and phonon density states of these phases are compared. Amorphous boron consists of distorted icosahedra, icosahedron fragments, and dioctahedra, connected by an amorphous network. The presence of metal atoms in amorphous BAM materials precludes the formation of icosahedra. For all the amorphous structures considered here, the Fermi level is located in the mobility gap independent of the number of valence electrons. The intra-icosahedral vibrations are localized in the range of 800 cm -1, whereas the inter-icosahedral vibrations appear at higher wavenumbers. The amorphization leads to an enhancement of the vibrations in the range of 1100–1250 cm -1. The mechanical properties of BAM materials are investigated at equilibrium and under shear and tensile strain. The anisotropy of the ideal shear and tensile strengths is explained in terms of a layered structure of the B 12 units. The strength of amorphous BAM materials is lower than that of themore » crystalline counterparts because of the partial fragmentation of the boron icosahedra in amorphous structures. The strength enhancement found experimentally for amorphous boron-based films is very likely related to an increase in film density, and the presence of oxygen impurities. For crystalline BAM materials, the icosahedra are preserved during elongation upon tension as well as upon shear in the (010)[100] slip system.« less

Authors:
 [1];  [2];  [3];  [1];  [4];  [5];  [6]
  1. NAS of Ukraine, Kyiv (Ukraine). Inst. of Problems for Material Sciences
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Technical Univ. of Munich (Germany). Dept. of Chemistry
  4. Jackson State Univ., Jackson, MS (United States). Dept. of Chemistry and Biochemistry and Interdisciplinary Center for Nanotoxicity
  5. Jackson State Univ., Jackson, MS (United States). Dept. of Chemistry and Biochemistry and Interdisciplinary Center for Nanotoxicity; Badger Technical Services, LLC, Vicksburg, MS (United States)
  6. USACE Engineer Research and Development Center (ERDC), Vicksburg, MS (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); Super Hard Materials (SHM), s.r.o., Sumperk (Czech Republic); Science and Technology Center in Ukraine (STCU), Kyiv (Ukraine)
OSTI Identifier:
1458625
Report Number(s):
LLNL-JRNL-736469
Journal ID: ISSN 0021-8979; 888343
Grant/Contract Number:  
AC52-07NA27344; 5964
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 119; Journal Issue: 20; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; boron; raman spectra; phonons; materials analysis; thin films; amorphous metals; amorphous state; crystal structure; hardness; stress strain relations

Citation Formats

Ivashchenko, V. I., Turchi, P. E. A., Veprek, S., Shevchenko, V. I., Leszczynski, Jerzy, Gorb, Leonid, and Hill, Frances. First-principles study of crystalline and amorphous AlMgB14-based materials. United States: N. p., 2016. Web. doi:10.1063/1.4952391.
Ivashchenko, V. I., Turchi, P. E. A., Veprek, S., Shevchenko, V. I., Leszczynski, Jerzy, Gorb, Leonid, & Hill, Frances. First-principles study of crystalline and amorphous AlMgB14-based materials. United States. doi:10.1063/1.4952391.
Ivashchenko, V. I., Turchi, P. E. A., Veprek, S., Shevchenko, V. I., Leszczynski, Jerzy, Gorb, Leonid, and Hill, Frances. Wed . "First-principles study of crystalline and amorphous AlMgB14-based materials". United States. doi:10.1063/1.4952391. https://www.osti.gov/servlets/purl/1458625.
@article{osti_1458625,
title = {First-principles study of crystalline and amorphous AlMgB14-based materials},
author = {Ivashchenko, V. I. and Turchi, P. E. A. and Veprek, S. and Shevchenko, V. I. and Leszczynski, Jerzy and Gorb, Leonid and Hill, Frances},
abstractNote = {Here, we report first-principles investigations of crystalline and amorphous boron and M1xM2yXzB14-z (M1, M2 = Al, Mg, Li, Na, Y; X = Ti, C, Si) phases (so-called “BAM” materials). Phase stability is analyzed in terms of formation energy and dynamical stability. The atomic configurations as well as the electronic and phonon density states of these phases are compared. Amorphous boron consists of distorted icosahedra, icosahedron fragments, and dioctahedra, connected by an amorphous network. The presence of metal atoms in amorphous BAM materials precludes the formation of icosahedra. For all the amorphous structures considered here, the Fermi level is located in the mobility gap independent of the number of valence electrons. The intra-icosahedral vibrations are localized in the range of 800 cm-1, whereas the inter-icosahedral vibrations appear at higher wavenumbers. The amorphization leads to an enhancement of the vibrations in the range of 1100–1250 cm-1. The mechanical properties of BAM materials are investigated at equilibrium and under shear and tensile strain. The anisotropy of the ideal shear and tensile strengths is explained in terms of a layered structure of the B12 units. The strength of amorphous BAM materials is lower than that of the crystalline counterparts because of the partial fragmentation of the boron icosahedra in amorphous structures. The strength enhancement found experimentally for amorphous boron-based films is very likely related to an increase in film density, and the presence of oxygen impurities. For crystalline BAM materials, the icosahedra are preserved during elongation upon tension as well as upon shear in the (010)[100] slip system.},
doi = {10.1063/1.4952391},
journal = {Journal of Applied Physics},
number = 20,
volume = 119,
place = {United States},
year = {Wed May 25 00:00:00 EDT 2016},
month = {Wed May 25 00:00:00 EDT 2016}
}

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