Dynamic Order-Disorder Transition in the S = ½ Kagome Antiferromagnets Barlowite and Claringbullite

2018 ◽  
Author(s):  
Alyssa Henderson ◽  
Lianyang Dong ◽  
Sananda Biswas ◽  
Hannah Revell ◽  
Yan Xin ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Density Functional Theory Calculations ◽  
Temperature Dependent ◽  
Orthorhombic Space Group ◽  
Functional Theory ◽  
Dynamic Disorder ◽  
Disorder Type

The nature of the structural phase transition in the quantum magnets barlowite, Cu4(OH)6FBr, and claringbullite, Cu4(OH)6FCl was investigated. These materials consist of parallel-stacked Cu2+ kagome layers, separated by planes that contain Cu2+ cations and halide anions. The structural transition is of an order-disorder type, where at ambient temperature the interlayer Cu2+ ions are disordered over three equivalent positions. In barlowite, the dynamic disorder becomes static as the temperature is decreased, resulting in a lowering of the overall symmetry from hexagonal P63/mmc to orthorhombic. The dynamic disorder in claringbullite persists to lower temperatures, with a transition to orthorhombic space group Pnma observed in some samples. Ab initio density functional theory calculations explain this temperature-dependent structural phase transition and provide additional insights regarding the differences between these two materials.

Dynamic Order-Disorder Transition in the S = ½ Kagome Antiferromagnets Barlowite and Claringbullite

2018 ◽  
Author(s):  
Alyssa Henderson ◽  
Lianyang Dong ◽  
Sananda Biswas ◽  
Hannah Revell ◽  
Yan Xin ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Density Functional Theory Calculations ◽  
Temperature Dependent ◽  
Orthorhombic Space Group ◽  
Functional Theory ◽  
Dynamic Disorder ◽  
Disorder Type

The nature of the structural phase transition in the quantum magnets barlowite, Cu4(OH)6FBr, and claringbullite, Cu4(OH)6FCl was investigated. These materials consist of parallel-stacked Cu2+ kagome layers, separated by planes that contain Cu2+ cations and halide anions. The structural transition is of an order-disorder type, where at ambient temperature the interlayer Cu2+ ions are disordered over three equivalent positions. In barlowite, the dynamic disorder becomes static as the temperature is decreased, resulting in a lowering of the overall symmetry from hexagonal P63/mmc to orthorhombic. The dynamic disorder in claringbullite persists to lower temperatures, with a transition to orthorhombic space group Pnma observed in some samples. Ab initio density functional theory calculations explain this temperature-dependent structural phase transition and provide additional insights regarding the differences between these two materials.

Janus monolayer of WSeTe, a new structural phase transition material driven by electrostatic gating

Nanoscale ◽  
2018 ◽  
Vol 10 (46) ◽  
pp. 21629-21633 ◽  
Author(s):  
Yajing Sun ◽  
Zhigang Shuai ◽  
Dong Wang
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Electrostatic Gating ◽  
Phase Transition Kinetics

By density functional theory calculations, we show that the Janus monolayer of WSeTe has faster semiconductor–semimetal phase transition kinetics than MoTe2.

scholarly journals DFT Calculations of the Structural, Mechanical, and Electronic Properties of TiV Alloy Under High Pressure

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 972 ◽  
Author(s):  
Fang Yu ◽  
Yu Liu
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Electronic Properties ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Applied Pressure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Dimensionless Ratio

A calculation program based on the density functional theory (DFT) is applied to study the structural, mechanical, and electronic properties of TiV alloys with symmetric structure under high pressure. We calculate the dimensionless ratio, elastic constants, shear modulus, Young’s modulus, bulk modulus, ductile-brittle transition, material anisotropy, and Poisson’s ratio as functions of applied pressure. Results suggest that the critical pressure of structural phase transition is 42.05 GPa for the TiV alloy, and structural phase transition occurs when the applied pressure exceeds 42.05 GPa. High pressure can improve resistance to volume change, as well as the ductility and atomic bonding, but the strongest resistances to elastic and shear deformation occur at P = 5   GPa for TiV alloy. Furthermore, the results of the density of states (DOS) indicate that the TiV alloy presents metallicity. High pressure disrupts the structural stability of the TiV alloy with symmetry, thereby inducing structural phase transition.

scholarly journals Strain-induced structural phase transition, electric polarization and unusual electric properties in photovoltaic materials CsMI3 (M = Pb, Sn)

RSC Advances ◽  
2020 ◽  
Vol 10 (21) ◽  
pp. 12432-12438
Author(s):  
Xiao-Rong Cheng ◽  
Xiao-Yu Kuang ◽  
Hao Cheng ◽  
Hao Tian ◽  
Si-Min Yang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Electric Polarization ◽  
Electric Properties ◽  
Functional Theory ◽  
Photovoltaic Materials ◽  
The Density Functional Theory ◽  
Photovoltaic Films

The structural phase transition, ferroelectric polarization, and electric properties have been investigated for photovoltaic films CsMI3 (M = Pb, Sn) epitaxially grown along (001) direction based on the density functional theory.

scholarly journals Predicted polymorph manipulation in an exotic double perovskite oxide

2019 ◽  
Vol 7 (39) ◽  
pp. 12306-12311 ◽  
Author(s):  
He-Ping Su ◽  
Shu-Fang Li ◽  
Yifeng Han ◽  
Mei-Xia Wu ◽  
Churen Gui ◽  
...  
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Double Perovskite ◽  
Density Functional Theory Calculations ◽  
Perovskite Oxide ◽  
Functional Theory ◽  
First Time ◽  
Perovskite Type

First-principles density functional theory calculations, for the first time, was used to predict the Mg3TeO6-to-perovskite type phase transition in Mn3TeO6 at around 5 GPa.

Conformational isomers of 1,2,5,6-tetrathiocins and the photoisomerization of a 1,2,5,6-tetrathiocin into a 1,2,3,6-tetrathiocin: X-ray structures of (C6X4S2)2 (X = F, Cl) and C6F4SSSC6F4S

1998 ◽  
Vol 76 (7) ◽  
pp. 1093-1101 ◽  
Author(s):  
Tristram Chivers ◽  
Masood Parvez ◽  
Ignacio Vargas-Baca ◽  
Gabriele Schatte
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Chair Conformation ◽  
Equilibrium Mixture ◽  
Orthorhombic Space Group ◽  
Functional Theory ◽  
Space Group ◽  
Conformational Isomers ◽  
High Yields ◽  
Twist Boat

The 1,2,5,6-tetrathiocins (C6X4S2)2 (3a, X = F; 3b, X = Cl) are obtained in high yields by the oxidation of the dithiols 1,2-C6X4(SH)2 (X = F, Cl) with I2 or SO2Cl2, respectively. In the solid state 3a has the C2h (chair) conformation and crystallizes in two different phases: alpha-(C6F4S2)2, monoclinic, P21/a, a = 9.351(2), b = 6.465(2), and c = 11.546(2) Å, ß = 95.60(1)°, V = 694.6(2) Å3, Z = 2; and ß-(C6F4S2)2, monoclinic, P21/c, a = 4.825(2), b = 11.302(2), and c = 12.453(2) Å, ß = 91.45(3)°, V = 678.8(3) Å3, Z = 2. By contrast, 3b displays a D2 (twist-boat) structure and crystallizes in the C2/c space group with a = 15.243(3), b = 8.703(2), and c = 27.010(14) Å, ß = 92.81(4)°, V = 3578(1) Å3, and Z = 8. The derivative 3a exists as an equilibrium mixture of two conformational isomers in toluene solution. The VT 19F NMR data afford the thermodynamic parameters H° = 9.9 ± 0.4 kJ mol-1 and S° = 14 ± 1 J K-1 mol-1. Density functional theory calculations for 3a indicate that the D2 conformation is lower in energy than the C2h isomer by 4.6 kJ mol-1. The photolysis of 3a in benzene promotes a transannular sulfur migration to give the 1,2,3,6-tetrathiocin, C6F4SSSC6F4S (6), which exists in a chair conformation with respect to antipodal sulfur atoms. Crystal structure of 6: orthorhombic, space group Pnma, a = 8.652(6), b = 19.084(4), and c = 8.301(6) Å, V = 1370.6(14) Å3, and Z = 4. The isomers 3a and 6 were also characterized by EI mass spectrometry, 19F NMR, FTIR, and Raman spectroscopies.Key words: tetrathiocins, conformational isomers, photoisomerization.

Structural phase transition, electronic, elastic, and vibrational properties of LiAl intermetallic compound: insights from first-principles calculations

2017 ◽  
Vol 95 (8) ◽  
pp. 691-698
Author(s):  
Y. Mogulkoc ◽  
Y.O. Ciftci ◽  
G. Surucu
Keyword(s):  
Phase Transition ◽  
Density Of States ◽  
Structural Phase Transition ◽  
First Principles ◽  
Density Functional ◽  
Structural Phase ◽  
Type Structure ◽  
Vibrational Properties ◽  
First Principles Calculations ◽  
Electronic Band

Using the first-principles calculations based on density functional theory (DFT), the structural, elastic, electronic, and vibrational properties of LiAl have been explored within the generalized gradient approximation (GGA) using the Vienna ab initio simulation package (VASP). The results demonstrate that LiAl compound is stable in the NaTl-type structure (B32) at ambient pressure, which is in good agreement with the experimental results and there is a structural phase transition from NaTl-type structure (B32) to CsCl-type structure (B2) at around 22.2 GPa pressure value. The pressure effects on the elastic properties have been discussed and the elastic property calculation indicates that the elastic instability could provide a phase transition driving force according to the variations relation of the elastic constant versus pressure. To gain further information about this, we also have investigated the other elastic parameters (i.e., Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and isotropic shear modulus). The electronic band structure, total and partial density of states, phonon dispersion curves, and one-phonon density of states of B2 and B32 phases are also presented with results.

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