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Author Nikolaev, A.V.; Michel, K.H. url  doi
openurl 
  Title Symmetry lowering at the structural phase transitions in NpO2 and UO2 Type A1 Journal article
  Year (down) 2003 Publication Physical review : B : condensed matter and materials physics Abbreviated Journal Phys Rev B  
  Volume 68 Issue 5 Pages 054112-054112,7  
  Keywords A1 Journal article; Condensed Matter Theory (CMT)  
  Abstract The structural phase transitions with electric-quadrupole long-range order in NpO2 (Fm (3) over barm-->Pn (3) over barm) and UO2 (Fm (3) over barm-->Pa (3) over bar) are analyzed from a group theoretical point of view. In both cases, the symmetry lowering involves three quadrupolar components belonging to the irreducible representation T-2g (Gamma(5)) of O-h and condensing in a triple-q structure at the X point of the Brillouin zone. The Pa (3) over bar structure is close to Pn (3) over barm, but allows for oxygen displacements. The Pa (3) over bar ordering leads to an effective electrostatic attraction between electronic quadrupoles while the Pn (3) over barm ordering results in a repulsion between them. It is concluded that the Pn (3) over barm structure can be stabilized only through some additional process such as strengthening of the chemical bonding between Np and O. We also derive the relevant structure-factor amplitudes for Pn (3) over barm and Pa (3) over bar, and the effect of domains on resonant x-ray scattering experiments.  
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  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000185240100038 Publication Date 2003-08-29  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0163-1829;1095-3795; ISBN Additional Links UA library record; WoS full record; WoS citing articles  
  Impact Factor 3.836 Times cited 15 Open Access  
  Notes Approved Most recent IF: 3.836; 2003 IF: NA  
  Call Number UA @ lucian @ c:irua:94847 Serial 3405  
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