Vibrational Dynamics of a Chiral Smectic Liquid Crystal Undergoing Vitrification and Cold Crystallization

Vibrational dynamics in the glass transition and the cold crystallization process of (S)-4′-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-benzoate (3F7HPhH7) was studied by Fourier transform infrared spectroscopy (FTIR) during cooling/heating experimental runs. The measured spectra processing was supported by quantum chemical density functional theory (DFT) calculations (frequency assignments). The perturbation-correlation moving window two-dimensional analysis (PCMW2D) was performed to examine how the height of individual absorption bands change under with temperature. Two-dimensional correlation analysis (2D-COS) was used to detect freezing-in or activation of the stochastic movements during the vitrification and the cold crystallization processes. Upon cooling, the vitrification process involves freezing-in of the stochastic movements of ester groups. Upon heating, as the cold crystallization process begins, the first to respond are the vibrations of the C–O–C and C=O groups in the rigid core.

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First-Principles Evaluation of the Potential of Borophene as a Monolayer Transparent Conductor

10.26434/chemrxiv.5439880 ◽

2017 ◽

Author(s):

Lyudmyla Adamska ◽

Sridhar Sadasivam ◽

Jonathan J. Foley ◽

Pierre Darancet ◽

Sahar Sharifzadeh

Keyword(s):

First Principles ◽

Density Functional ◽

State Of The Art ◽

Transparent Electrode ◽

Visible Range ◽

Two Dimensional ◽

Transparent Conductor ◽

Many Body ◽

Functional Theory ◽

Many Body Perturbation Theory

Two-dimensional boron is promising as a tunable monolayer metal for nano-optoelectronics. We study the optoelectronic properties of two likely allotropes of two-dimensional boron using first-principles density functional theory and many-body perturbation theory. We find that both systems are anisotropic metals, with strong energy- and thickness-dependent optical transparency and a weak (<1%) absorbance in the visible range. Additionally, using state-of-the-art methods for the description of the electron-phonon and electron-electron interactions, we show that the electrical conductivity is limited by electron-phonon interactions. Our results indicate that both structures are suitable as a transparent electrode.

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Complex magnetism of the two-dimensional antiferromagnetic Ge2F: from a Néel spin-texture to a potential antiferromagnetic skyrmion

RSC Advances ◽

10.1039/d0ra09678d ◽

2021 ◽

Vol 11 (15) ◽

pp. 8654-8663

Author(s):

Fatima Zahra Ramadan ◽

Flaviano José dos Santos ◽

Lalla Btissam Drissi ◽

Samir Lounis

Keyword(s):

Density Functional Theory ◽

Magnetic Properties ◽

Density Functional ◽

Low Energy ◽

Two Dimensional ◽

Functional Theory ◽

2D Material ◽

Energy Models ◽

Spin Texture

Based on density functional theory combined with low-energy models, we explore the magnetic properties of a hybrid atomic-thick two-dimensional (2D) material made of germanene doped with fluorine atoms in a half-fluorinated configuration (Ge2F).

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Two-dimensional g-C3N4/Ti2CO2 heterostructure as a direct Z-scheme photocatalyst for water splitting: A hybrid density functional theory investigation

Physica E Low-dimensional Systems and Nanostructures ◽

10.1016/j.physe.2021.114872 ◽

2021 ◽

pp. 114872

Author(s):

X. Liu ◽

W. Kang ◽

L. Qi ◽

J. Zhao ◽

Y. Wang ◽

...

Keyword(s):

Density Functional Theory ◽

Water Splitting ◽

Density Functional ◽

Hybrid Density Functional Theory ◽

Two Dimensional ◽

Functional Theory ◽

Hybrid Density Functional

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Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters

Scientific Reports ◽

10.1038/s41598-021-95551-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Christian Wiebeler ◽

Joachim Vollbrecht ◽

Adam Neuba ◽

Heinz-Siegfried Kitzerow ◽

Stefan Schumacher

Keyword(s):

Absorption Spectra ◽

Density Functional ◽

Energy Levels ◽

Spectroscopic Properties ◽

Absorption Bands ◽

Functional Theory ◽

Vertical Excitation ◽

Hartree Fock ◽

Tauc Plot ◽

Electrochemical Approach

AbstractA detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.

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