Temperature-Dependent Raman Study of the Smectic to Nematic Phase Transition and Vibrational Analysis Using Density Functional Theory of the Liquid Crystalline System 4-Decyloxy Benzoic Acid

2010 ◽  
Vol 64 (2) ◽  
pp. 187-194 ◽  
Author(s):  
K. Vikram ◽  
Nicolae Tarcea ◽  
J. Popp ◽  
Ranjan K. Singh
Keyword(s):  
Phase Transition ◽  
Nematic Phase ◽  
Density Functional ◽  
Liquid Crystalline ◽  
Vibrational Analysis ◽  
Temperature Dependent ◽  
Functional Theory ◽  
Raman Study ◽  
Crystalline System ◽  
Liquid Crystalline System

scholarly journals The Origin of the Helical Twist Inversion in Single Component Cholesteric Liquid Crystals

1994 ◽  
Vol 49 (11) ◽  
pp. 1081-1086 ◽  
Author(s):  
I. Dierking ◽  
F. Gießelmann ◽  
P. Zugenmaier ◽  
K. Mohr ◽  
H. Zaschke ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Single Component ◽  
Power Model ◽  
Temperature Dependent ◽  
First Approximation ◽  
Helical Twist ◽  
Chiral Centers ◽  
Crystalline System ◽  
The Individual ◽  
Liquid Crystalline System

Abstract The cholesteric twist inversion by temperature variation o f a single component thermotropic liquid crystalline system was experimentally investigated and is explained by the partial twisting power model, evaluating the temperature dependent pitch o f five different configurations of a benzoic acid biphenyl ester with two chiral centers. The temperature dependence o f the twisting power and the cholesteric pitch for several stereoisomeric compounds can in first approximation be predicted by the partial twisting powers of the individual chiral centers determined from the partially racemic configurations.

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.

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