Topological phase transition associated with structural phase transition in ternary half Heusler compound LiAuBi.

Author(s):  
Anita Yadav ◽  
Shailesh Kumar ◽  
Manoharan Muruganathan ◽  
Rakesh Kumar

Abstract In this article, we report detailed theoretical investigations of topological phases in a new non-centrosymmetric half Heusler compound LiAuBi upto a pressure of 30 GPa. It is found that the compound forms into a dynamically stable face centered cubic (FCC) lattice structure of space group F ¯43m (216) at ambient pressure. The compound is topologically non-trivial at ambient pressure, but undergoes a quantum phase transition to trivial topological phase at 23.4 GPa. However, the detailed investigations show a structural phase transition from FCC lattice (space group 216) to a honeycomb lattice (space group 194) at 13 GPa, which is also associated with a non-trivial to trivial topological phase transition. Further investigations show that the compound also carries appreciable thermoelectric properties at ambient pressure. The figure of merit (ZT) increases from 0.21 at room temperature to a maximum value of 0.22 at 500K. The theoretical findings show its potential for practical applications in spintronics as well as thermoelectricity, therefore LiAuBi needs to be synthesized and investigated experimentally for its applications.

2014 ◽  
Vol 30 ◽  
pp. 6-10 ◽  
Author(s):  
Lilia S. Xie ◽  
Leslie M. Schoop ◽  
Sergey A. Medvedev ◽  
Claudia Felser ◽  
R.J. Cava

2018 ◽  
Vol 51 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Federico Serrano-Sánchez ◽  
Norbert M. Nemes ◽  
José Luis Martínez ◽  
Oscar Juan-Dura ◽  
Marco Antonio de la Torre ◽  
...  

Thermoelectric materials are expected to become new alternative sources of sustainable energy. Among them, the SnSe intermetallic alloy has been described as an excellent thermoelectric compound, characterized by an extremely low thermal conductivity with maximum performance at the onset of a structural phase transition at 800 K. Recently, novel SnSe derivatives with Ge substitution have been synthesized by a direct arc-melting technique. This produces nanostructured polycrystalline samples that exhibit a record high Seebeck coefficient, anticipating an excellent performance above room temperature. Here, the structural phase transition from a GeS-type structure (space groupPnma) to a TlI-type structure (space groupCmcm) is investigatedin situ vianeutron powder diffraction (NPD) in the temperature range 298–853 K for the selected composition Sn0.8Ge0.2Se. This transition takes place at 803 K, as shown by differential scanning calorimetry. The analysis from the NPD data shows a non-monotonic behaviour of the anisotropic displacement parameters upon entering the domain of theCmcmstructure. The energies of the atomic vibrations have been quantitatively analysed by fitting the temperature-dependent mean-square displacements to Einstein oscillators. The thermal conductivity of Sn0.8Ge0.2Se is as low as 0.35 W m−1 K−1at 773 K, which mostly represents the lattice thermal contribution.


2006 ◽  
Vol 61 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Ingrid Svoboda ◽  
Hartmut Fuess ◽  
Thorsten M. Gesing ◽  
...  

The crystal structures of piperazinium tetrahalogenometallates (II) [C4H12N2]MX4(M = Zn, Hg; X = Br, I), orthorhombic with space group P212121 and Z = 4 are isostructural with [C4H12N2]CdI4. The structure consists of piperazinium cations and isolated tetrahedralMX4 anions. [C4H12N2]ZnBr4 (1): a = 850.4(2), b = 1146.5(3), and c = 1228.4(4) pm at 300(2) K, [C4H12N2]ZnI4 (2): a = 886.89(6), b = 1209.11(9), and c = 1293.79(9) pm at 223(2) K, [C4H12N2]HgBr4 (3): a = 865.48(14), b = 1158.7(3), and c = 1233.3(2) pm at 293(2) K, [C4H12N2]HgI4 (4): a = 899.6(2), b = 1230.0(2), and c = 1299.5(3) pm at 293(2) K. All crystals show a structural phase transition at about 560 K and decomposition temperatures above 600 K. The lattice stability of the crystals is well explained by N-H · · · X hydrogen bond networks.


2020 ◽  
Vol 22 (8) ◽  
pp. 4602-4609
Author(s):  
Raghottam M. Sattigeri ◽  
Sharad Babu Pillai ◽  
Prafulla K. Jha ◽  
Brahmananda Chakraborty

Half-Heusler compound LiMgBi exhibits pressure driven Topological Insulating (TI) nature with robust spin-locked dissipationless Fermion transport along the surface states.


2014 ◽  
Vol 1047 ◽  
pp. 147-150
Author(s):  
Yeshvir Singh Panwar ◽  
Mahendra Aynyas ◽  
M.K. Tejraj ◽  
S.P. Sanyal

We report ab initio calculations of pressure induced structural phase transition and electronic properties of thulium nitride (TmN). The total energy as a function of volume is obtained by using the self-consistent tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). It is found that TmN is stable in NaCl – type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B1-phase) structure to CsCl-type (B2-phase) structure of this compound at a high pressure of 68 GPa. We also calculate the lattice parameter (a0), bulk modulus (B0), band structure and density of states. From energy band diagram it is observed that TmN exhibit metallic behaviour. The calculated values of equilibrium lattice parameter and bulk modulus are in general good agreement with available experimental data.


Author(s):  
Ekaterina S. Smirnova ◽  
Olga A. Alekseeva ◽  
Alexander P. Dudka ◽  
Dmitry N. Khmelenin ◽  
Kirill V. Frolov ◽  
...  

An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3(BO3)4 between 11 and 500 K has revealed structural phase transition at T str = 365 K. The Bi atoms enter the composition from Bi2Mo3O12-based flux during crystal growth and significantly affect T str. The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96Bi0.04)Fe3(BO3)4. In the low-temperature (LT) phase below T str the (Ho0.96Bi0.04)Fe3(BO3)4 crystal symmetry is trigonal, of space group P3121, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32. There is a sharp jump of oxygen O1 (LT) and O2 (LT) atomic displacement parameters (ADP) at T str. O1 and O2 ADP ellipsoids are the most elongated over 90–500 K. In space group R32 specific distances decrease steadily or do not change with decreasing temperature. In space group P3121 the distortion of the polyhedra Ho(Bi)O6, Fe1O6 and Fe2O6, B2O3 and B3O3 increases with decreasing temperature, whereas the triangles B1O3 remain almost equilateral. All BO3 triangles deviate from the ab plane with decreasing temperature. Fe–Fe distances in Fe1 chains decrease, while distances in Fe2 chains increase with decreasing temperature. The Mössbauer study confirms that the FeO6 octahedra undergo complex dynamic distortions. However, all observed distortions are rather small, and the general change in symmetry during the structural phase transition has very little influence on the local environment of iron in oxygen octahedra. The Mössbauer spectra do not distinguish two structurally different Fe1 and Fe2 positions in the LT phase. The characteristic temperatures of cation thermal vibrations were calculated using X-ray diffraction and Mössbauer data.


2013 ◽  
Vol 1528 ◽  
Author(s):  
Kazutaka G. Nakamura ◽  
Jianbo Hu ◽  
Kouhei Ichiyanagi ◽  
Nobuaki Kawai ◽  
Shin-ichi Adachi

ABSTRACTDynamics of structural phase transition in polycrystalline samples (tetragonal stabilized zirconia and bismuth) under laser-shock compression has been studied using nanosecond time-resolved X-ray diffraction technique based on synchrotron radiation. Tetragonal zirconia shows the structural phase transition to the monoclinic phase within 20 ns during shock compression without any intermediate and reverts back to the tetragonal phase during pressure release. Bismuth shows more complex phase transition dynamics. The Bi-I phase, which is the stable phase at ambient pressure and temperature, transfers to Bi-V phase within 4 ns under shock compression and gradually reverts back following the path of Bi-V →Bi-III → Bi-II → Bi-I within 30 ns during pressure release.


2009 ◽  
Vol 65 (4) ◽  
pp. 509-515 ◽  
Author(s):  
Eric J. Chan ◽  
A. David Rae ◽  
T. Richard Welberry

A low-temperature structural phase transition has been observed for form (II) of benzocaine (BZC). Lowering the temperature doubles the b-axis repeat and changes the space group from P212121 to P1121 with γ now 99.37 °. The structure is twinned, the twin rule corresponding to a 21 screw rotation parallel to a. The phase transition is associated with a sequential displacement parallel to a of zigzag bi-layers of ribbons perpendicular to b*. No similar phase transition was observed for form (I) and this was attributed to the different packing symmetries of the two room-temperature polymorphic forms.


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