Stable Compound of Helium and Sodium at High Pressure (Abstract/Comunicazione in rivista)

Type
Label
  • Stable Compound of Helium and Sodium at High Pressure (Abstract/Comunicazione in rivista) (literal)
Anno
  • 2014-01-01T00:00:00+01:00 (literal)
Alternative label
  • G. Saleh, X. Dong, A. Oganov, C. Gatti, G. Qian, Q. Zhu, X. Zhou, H. Wang (2014)
    Stable Compound of Helium and Sodium at High Pressure
    (literal)
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  • G. Saleh, X. Dong, A. Oganov, C. Gatti, G. Qian, Q. Zhu, X. Zhou, H. Wang (literal)
Pagina inizio
  • C617 (literal)
Pagina fine
  • C617 (literal)
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  • conferenza selected from contributed abstracts and delivered by Gabriele Saleh, XXIII IUCr Triennial Congress, 5-12 August 2014 Montreal, Canada (literal)
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  • A70 (literal)
Rivista
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  • 1 (literal)
Note
  • Comunicazione (literal)
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  • Moscow Institute of Physics and Technology, Dolgoprudny, Russia , 2 School of Physics and MOE Key Laboratory of Weak - Light Nonlinear Photonics, Tianjin, China , 3 Center for Materials by Design, Department of Geosciences, Stony Brook, USA , 4 Istituto di Scienze e Tecnologie Molecolari, National Research Council, Milano, Italy , 5 National Laboratory of Solid State Microstructures, Nanjing, China , 6 School of Mat erials Science, Northwestern Polytechnical University, Xi'an, China , 7 Center for Materials Crystallography, Aarhus, Denmar (literal)
Titolo
  • Stable Compound of Helium and Sodium at High Pressure (literal)
Abstract
  • Microsymposium MS41.O04 Stable Compound of Helium and Sodium at High Pressure G. Saleh 1 , X. Dong 2,3 , A. Oganov 1,3,6 , C. Gatti 4,7 , G. Qian 3 , Q. Zhu 3 , X. Zhou 2,3 , H. Wang 2,5 1 Moscow Institute of Physics and Technology, Dolgoprudny, Russia , 2 School of Physics and MOE Key Laboratory of Weak - Light Nonlinear Photonics, Tianjin, China , 3 Center for Materials by Design, Department of Geosciences, Stony Brook, USA , 4 Istituto di Scienze e Tecnologie Molecolari, National Research Council, Milano, Italy , 5 National Laboratory of Solid State Microstructures, Nanjing, China , 6 School of Mat erials Science, Northwestern Polytechnical University, Xi'an, China , 7 Center for Materials Crystallography, Aarhus, Denmark Helium (He) is, on par with Neon, the most inert element in the Periodic Table. Indeed, no conclusive proofs about stable com pounds containing chemical bonds with He at ambient conditions have been reported so far. However, pressure significantly affects ch emical properties of elements. By using USPEX [1], a software which has been successfully used in the past to predict unexpected h igh pressure crystal structure [1], we found that above 160 GPa He and Sodium exothermically combine to form the compound Na2He, whose structure is reported in Fig. 1. Quasiharmonic free energy calculations based on computed phonon spectra indicate that th e free energy of formation of Na2He is negative and that the latter is barely affected by the temperature (0 - 800 K range was considered). In order to understand the cause of stability of Na2He, we carried out a thorough study of its electronic struct ure at various pressures by means of several different approaches including the examination of the band structure and the analysis o f real - space descriptors such as the electron density in the framework of the Quantum Theory of Atoms in Molecules [2], the Electr on Localization Function [3] and the deformation density. By examining the band structure, we found that such compound is an ins ulator whose band - gap increases with pressure. Regarding real - space descriptors, two remarkable features of Na2He are the negati ve charge on He (obtained both using Mulliken and Bader partitioning) and the presence of interstitially localized electrons (i. e. Non - Nuclear Attractors), the latter being detectable in all the analyses above mentioned. In the range 160 - 350 GPa, the exoth ermicity associated to the formation of Na2He is mainly due to the volume reduction, while at higher pressures the electronic energy p lays a prominent role in the stabilization of this compound. In this contribution we present the results of our study with particular emphasis on the role played by He in the stabilization of Na2He. (literal)
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