scholarly journals Terbium-induced phase transitions and weak ferromagnetism in multiferroic bismuth ferrite ceramics

2017 ◽  
Vol 5 (10) ◽  
pp. 2669-2685 ◽  
Author(s):  
Vladimir Koval ◽  
Ivan Skorvanek ◽  
Juraj Durisin ◽  
Giuseppe Viola ◽  
Alexandra Kovalcikova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Bismuth Ferrite ◽  
Weak Ferromagnetism ◽  
Promising Candidate

The increasing addition of Tb in the system Bi1−xTbxFeO3 produces a progressive modification of the crystal structure from rhombohedral R3c to orthorhombic Pnma which results in the appearance and enhancement of the net magnetization, with the composition x ≈ 0.15–0.20 being a promising candidate for magnetoelectric applications.

Crystal structure, compressibility and possible phase transitions in \boldvarepsilon-FeSi studied by first-principles pseudopotential calculations

1999 ◽  
Vol 55 (4) ◽  
pp. 484-493 ◽  
Author(s):  
Lidunka Vočadlo ◽  
Geoffrey D. Price ◽  
I. G. Wood
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Stable Phase ◽  
Third Order ◽  
First Derivative ◽  
Pseudopotential Calculations ◽  
Cscl Type ◽  
Murnaghan Equation

An investigation of the relative stability of the FeSi structure and of some hypothetical polymorphs of FeSi has been made by first-principles pseudopotential calculations. It has been shown that the observed distortion from ideal sevenfold coordination is essential in stabilizing the FeSi structure relative to one of the CsCl type. Application of high pressure to FeSi is predicted to produce a structure having nearly perfect sevenfold coordination. However, it appears that FeSi having a CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 13 GPa. Fitting of the calculated internal energy vs volume for the FeSi structure to a third-order Birch–Murnaghan equation of state led to values, at T = 0 K, for the bulk modulus, K 0, and for its first derivative with respect to pressure, K 0′, of 227 GPa and 3.9, respectively.

79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide

1989 ◽  
Vol 44 (1) ◽  
pp. 41-55 ◽  
Author(s):  
Jutta Hartmann ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Temperature Range

Abstract The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.

scholarly journals Crystal structure, phase transitions and vibrations of H2O molecules in [Ca(H2O)2](ReO4)2

2017 ◽  
Vol 131 (1) ◽  
pp. 479-489 ◽  
Author(s):  
Joanna Hetmańczyk ◽  
Łukasz Hetmańczyk ◽  
Wojciech Nitek
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Structure Phase
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