Vibrational dynamics in glassy crystals. Raman and DSC studies of equilibrium and non-equilibrium structures of phenylacetylene in methylcyclohexane

2002 ◽  
Vol 280 (1-2) ◽  
pp. 153-161 ◽  
Author(s):  
H. Abramczyk ◽  
B. Brożek ◽  
S. Kuberski
Keyword(s):  
Vibrational Dynamics ◽  
Dsc Studies ◽  
Equilibrium Structures ◽  
Glassy Crystals ◽  
Non Equilibrium

BAND NN: A Deep Learning Framework For Energy Prediction and Geometry Optimization of Organic Small Molecules

2019 ◽  
Author(s):  
Siddhartha Laghuvarapu ◽  
Yashaswi Pathak ◽  
U. Deva Priyakumar
Keyword(s):  
Machine Learning ◽  
Density Functional ◽  
Computational Cost ◽  
Geometry Optimization ◽  
Dft Methods ◽  
Energy Prediction ◽  
Machine Learning Model ◽  
Equilibrium Structures ◽  
High Level ◽  
Non Equilibrium

Recent advances in artificial intelligence along with development of large datasets of energies calculated using quantum mechanical (QM)/density functional theory (DFT) methods have enabled prediction of accurate molecular energies at reasonably low computational cost. However, machine learning models that have been reported so far requires the atomic positions obtained from geometry optimizations using high level QM/DFT methods as input in order to predict the energies, and do not allow for geometry optimization. In this paper, a transferable and molecule-size independent machine learning model (BAND NN) based on a chemically intuitive representation inspired by molecular mechanics force fields is presented. The model predicts the atomization energies of equilibrium and non-equilibrium structures as sum of energy contributions from bonds (B), angles (A), nonbonds (N) and dihedrals (D) at remarkable accuracy. The robustness of the proposed model is further validated by calculations that span over the conformational, configurational and reaction space. The transferability of this model on systems larger than the ones in the dataset is demonstrated by performing calculations on select large molecules. Importantly, employing the BAND NN model, it is possible to perform geometry optimizations starting from non-equilibrium structures along with predicting their energies.

scholarly journals Tunable thermo-reversible bicontinuous nanoparticle gel driven by the binary solvent segregation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuyin Xi ◽  
Ronald S. Lankone ◽  
Li-Piin Sung ◽  
Yun Liu
Keyword(s):  
Phase Separation ◽  
Domain Size ◽  
Binary Solvent ◽  
Colloidal Systems ◽  
Colloidal Assembly ◽  
Structures And Properties ◽  
Wide Range ◽  
Equilibrium Process ◽  
Equilibrium Structures ◽  
Non Equilibrium

AbstractBicontinuous porous structures through colloidal assembly realized by non-equilibrium process is crucial to various applications, including water treatment, catalysis and energy storage. However, as non-equilibrium structures are process-dependent, it is very challenging to simultaneously achieve reversibility, reproducibility, scalability, and tunability over material structures and properties. Here, a novel solvent segregation driven gel (SeedGel) is proposed and demonstrated to arrest bicontinuous structures with excellent thermal structural reversibility and reproducibility, tunable domain size, adjustable gel transition temperature, and amazing optical properties. It is achieved by trapping nanoparticles into one of the solvent domains upon the phase separation of the binary solvent. Due to the universality of the solvent driven particle phase separation, SeedGel is thus potentially a generic method for a wide range of colloidal systems.

scholarly journals Distinguishing between Clausius, Boltzmann and Pauling Entropies of Frozen Non-Equilibrium States

Entropy ◽  
2019 ◽  
Vol 21 (8) ◽  
pp. 799 ◽  
Author(s):  
Rainer Feistel
Keyword(s):  
Heat Capacity ◽  
Historical Review ◽  
Zero Point ◽  
Quantum States ◽  
Boltzmann Entropy ◽  
Nernst Theorem ◽  
Symbolic Information ◽  
Equilibrium Structures ◽  
Physical Quantities ◽  
Non Equilibrium

In conventional textbook thermodynamics, entropy is a quantity that may be calculated by different methods, for example experimentally from heat capacities (following Clausius) or statistically from numbers of microscopic quantum states (following Boltzmann and Planck). It had turned out that these methods do not necessarily provide mutually consistent results, and for equilibrium systems their difference was explained by introducing a residual zero-point entropy (following Pauling), apparently violating the Nernst theorem. At finite temperatures, associated statistical entropies which count microstates that do not contribute to a body’s heat capacity, differ systematically from Clausius entropy, and are of particular relevance as measures for metastable, frozen-in non-equilibrium structures and for symbolic information processing (following Shannon). In this paper, it is suggested to consider Clausius, Boltzmann, Pauling and Shannon entropies as distinct, though related, physical quantities with different key properties, in order to avoid confusion by loosely speaking about just “entropy” while actually referring to different kinds of it. For instance, zero-point entropy exclusively belongs to Boltzmann rather than Clausius entropy, while the Nernst theorem holds rigorously for Clausius rather than Boltzmann entropy. The discussion of those terms is underpinned by a brief historical review of the emergence of corresponding fundamental thermodynamic concepts.

Vibrational dynamics of crystalline silicon dioxide with charged Ge impurities

2016 ◽  
Vol 30 (30) ◽  
pp. 1650206
Author(s):  
A. N. Kislov
Keyword(s):  
Silicon Dioxide ◽  
Atomic Structure ◽  
Lattice Dynamics ◽  
Crystalline Silicon ◽  
Local Density ◽  
Local Atomic Structure ◽  
Vibrational States ◽  
Vibrational Dynamics ◽  
Equilibrium Structures ◽  
Localized Vibrations

The effects of differently charged Ge impurities on the local atomic structure and lattice dynamics of [Formula: see text]-quartz were studied. We have determined the equilibrium structures and calculated the symmetrized local density of vibrational states for the Ge-doped [Formula: see text]-quartz. The frequencies of localized vibrations of [Formula: see text]- and [Formula: see text]-symmetries induced by Ge impurities were obtained. Besides, we have analyzed what contribution the vibrations of atoms located around the Ge impurities make to the localized symmetrized vibrations.

Non-equilibrium structures and geometry relaxation in polyoctylthiophene

1990 ◽  
Vol 172 (2) ◽  
pp. 143-146 ◽  
Author(s):  
G. Zerbi ◽  
L. Castellani ◽  
B. Chierichetti ◽  
C. Gallazzi ◽  
O. Ingänas
Keyword(s):  
Equilibrium Structures ◽  
Non Equilibrium
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