scholarly journals О термической устойчивости некоторых квазифуллеренов

2019 ◽  
Vol 61 (3) ◽  
pp. 604
Author(s):  
А.И. Подливаев ◽  
Л.А. Опенов
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Thermal Stability ◽  
Frequency Factor ◽  
Arrhenius Law ◽  
Method Of Molecular Dynamics ◽  
Temperature Dependences ◽  
Thermal Stability Of

AbstractThe thermal stability of recently predicted quasi-fullerenes С_20, С_42, С_48, and С_60 is studied by the method of molecular dynamics. The routes of their decomposition and the temperature dependences of their lifetimes are determined. The activation energy and frequency factor values that appear in the Arrhenius law are found. New isomers are detected.

scholarly journals Цепочки карбинофуллеренов C-=SUB=-20-=/SUB=-

2019 ◽  
Vol 61 (4) ◽  
pp. 793
Author(s):  
А.И. Подливаев ◽  
Л.А. Опенов
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Thermal Stability ◽  
Computer Simulation ◽  
Binding Energies ◽  
Decay Process ◽  
Arrhenius Law ◽  
Carbon Structure ◽  
One Dimensional ◽  
Method Of Molecular Dynamics

AbstractThe results of computer simulation of a new one-dimensional carbon structure representing chains composed of C_20 carbinofullerenes are presented. Their binding energies are determined. Their thermal stability is studied by the method of molecular dynamics. The resistance of chains to stretching is also studied. It is shown that breaking the bond between adjacent carbinofullerene moieties in the chain is a preferred channel for thermal and deformational destruction. The ultimate strains of chains and also the temperature dependence of their lifetime until the time of decay are determined. Using different approaches, the activation energy values and the frequency factors of the decay process in the Arrhenius law are found.

scholarly journals Термическая устойчивость карбинофуллеренов C-=SUB=-38-=/SUB=-, C-=SUB=-62-=/SUB=- и C-=SUB=-64-=/SUB=-

2020 ◽  
Vol 62 (6) ◽  
pp. 979
Author(s):  
А.И. Подливаев
Keyword(s):  
Molecular Dynamics ◽  
Thermal Stability ◽  
Activation Energies ◽  
Molecular Dynamics Method ◽  
Thermally Stable ◽  
Arrhenius Law ◽  
Temperature Dependences ◽  
Dynamics Method ◽  
Thermal Stability Of

Abstract The thermal stability of recently predicted carbinofullerenes C_38, C_62, and C_64 was examined using the molecular dynamics method. Their decomposition channels and temperature dependences of the lifetime were characterized. The activation energies and frequency factors in the Arrhenius law were determined. New isomers of carbinofullerenes C_38 and C_62, which are more thermally stable than the initial carbinofullerenes, were found.

Meyer-Neldel Rule on thermal stability parameters (trap depth and frequency factor) of luminescence signals in quartz

2021 ◽  
Author(s):  
Zuzanna Kabacińska ◽  
Alida Timar-Gabor ◽  
Benny Guralnik
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Hydrogen Diffusion ◽  
Dose Range ◽  
Accurate Determination ◽  
Frequency Factor ◽  
Proton Conduction ◽  
High Dose ◽  
Compensation Law ◽  
Thermal Stability Of

<p>Thermally activated processes can be described mathematically by the Arrhenius equation. The Meyer-Neldel Rule (MNR), or compensation law, linearly relates the pre-exponent term to the logarithm of the excitation enthalpy for processes that are thermally driven in an Arrhenian manner. This empirical rule was observed in many areas of materials science, in physics, chemistry, and biology. In geosciences it was found to uphold in hydrogen diffusion (Jones 2014a) and proton conduction (Jones 2014b) in minerals.</p><p>Trapped charge dating methods that use electron spin resonance (ESR) or optically or thermally stimulated luminescence (OSL and TL) are based on the dose-dependent accumulation of defects in minerals such as quartz and feldspar. The thermal stability of these defects in the age range investigated is a major prerequisite for accurate dating, while the accurate determination of the values of the trap depths and frequency factors play a major role in thermochronometry applications. </p><p>The correlation of kinetic parameters for diffusion has been very recently established for irradiated oxides (Kotomin et al. 2018). A correlation between the activation energy and the frequency factor that satisfied the Meyer–Neldel rule was reported when the thermal stability of [AlO<sub>4</sub>/h<sup>+</sup>]<sup>0</sup> and [TiO<sub>4</sub>/M<sup>+</sup>]<sup>0</sup> ESR signals in quartz was studied as function of dose (Benzid and Timar-Gabor 2020). Here we compiled the optically stimulated luminescence (OSL) data published so far in this regard, and investigated experimentally the thermal stability of OSL signals for doses ranging from 10 to 10000 Gy in sedimentary quartz samples. We report a linear relationship between the natural logarithm of the preexponent term (the frequency factor) and the activation energy E, corresponding to a Meyer-Neldel energy of 45 meV, and a deviation from first order kinetics in the high dose range accompanied by an apparent decrease in thermal stability. The implications of these observations and the atomic and physical mechanisms are currently studied.</p><p> </p><p><strong>References</strong></p><p>Benzid, K., Timar Gabor, A. 2020. The compensation effect (Meyer–Neldel rule) on [AlO<sub>4</sub>/h<sup>+</sup>]<sup>0</sup> and [TiO<sub>4</sub>/M<sup>+</sup>]<sup>0</sup> paramagnetic centers in irradiated sedimentary quartz. <em>AIP Advance</em>s 10, 075114.</p><p>Kotomin, E., Kuzovkov, V., Popov, A. I., Maier, J., and Vila, R. 2018. Anomalous kinetics of diffusion-controlled defect annealing in irradiated ionic solids. <em>J. Phys. Chem. A</em> 122(1), 28–32</p><p>Jones, A. G. (2014a), Compensation of the Meyer-Neldel Compensation Law for H diffusion in minerals, <em>Geochem. Geophys. Geosyst.</em>, 15, 2616–2631</p><p>Jones, A. G. (2014b), Reconciling different equations for proton conduction using the Meyer-Neldel compensation rule, <em>Geochem. Geophys. Geosyst</em>., 15, 337–349</p>

scholarly journals Цепочки карбин-карбинофуллеренов C-C-=SUB=-20-=/SUB=-

2019 ◽  
Vol 61 (12) ◽  
pp. 2521
Author(s):  
Л.А. Опенов ◽  
А.И. Подливаев
Keyword(s):  
Molecular Dynamics ◽  
Thermal Stability ◽  
Computer Simulation ◽  
Bond Energy ◽  
Decay Process ◽  
Arrhenius Law ◽  
Carbon Structure ◽  
One Dimensional ◽  
Method Of Molecular Dynamics ◽  
The Stability

The results of computer simulation of a new one-dimensional carbon structure - chains consisting of C20 carbinofullerenes linked by carbon atoms are presented. Their bond energy values are determined. Their thermal stability is studied by the method of molecular dynamics. The stability of chains to tension was also investigated and compared with the stability of chains of C20 carbynofullerenes without intermediate carbon atoms. It has been shown that the preferred channel of thermal decay is the fusing of neighboring carbynofullerenes, and the deformation channel is the separation of the extreme carbinofullerene from the chain. The ultimate strains of chains and also the temperature dependence of their lifetime until the time of decay are determined. The values of activation energies and frequency factors of the decay process in the Arrhenius law are found.

scholarly journals Crystallization, mechanical and electrochemical behavior of Al-Ce-TM (TM = Fe, Co, Ni and Cu) amorphous alloys

2019 ◽  
Vol 4 (2) ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Electrochemical Behavior ◽  
Amorphous Alloys ◽  
Frequency Factor ◽  
Onset Crystallization Temperature ◽  
Nano Crystalline ◽  
Thermal Stability Of

Al86Ce10TM4 amorphous alloys (TM=Fe, Co, Ni and Cu) were fabricated using melt-spin fast-quenching method. The crystallization, mechanical and electrochemical behavior of the as-spun and the post-annealed alloys were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro-indentation and electrochemical techniques. It was found the completely amorphous Al86Ce10TM4 alloys (TM=Fe, Co, Ni and Cu) go through two crystallization processes, where the first exothermal peak represents nucleation of nano-crystalline particles and the second exothermal peak signifies growth of the nano-crystalline precipitates. Both the nucleation and growth processes rely on diffusion-controlled mechanism. The first onset crystallization temperature Tx1 associated with activation energy E1 and frequency factor Ko1 can be used to evaluate the thermal stability of the amorphous alloys while the second onset crystallization temperature Tx2 associated with activation energy E2 and frequency factor Ko2 can be taken to judge the thermal stability of ideal amorphous-nanocrystalline mixed structure in sustaining optimized mechanical and electrochemical properties. The as-spun and post-annealed alloys exhibit higher mechanical hardness (860~1180 MPa), corrosion resistance (10-8A/cm2 ) and high temperature endurance (284, 300 and 420°C for Al86Ce10Co4 , Al86Ce10Ni4 andAl86Ce10Fe4 , respectively) compared to hardness 500~600 MPa, corrosion resistance 10-7A/cm2 and high temperature durability 200°C of traditional Al crystalline alloys, manifesting the value on scientific studies and engineering applications of the Al86Ce10TM4 amorphous alloys.

Simulation of Thermal Stability and Friction: A Lubricant Confined Between Monolayers of Wear Inhibitors on Iron Oxide

1998 ◽  
Vol 543 ◽  
Author(s):  
T. Çağin ◽  
Y. Zhou ◽  
E. S. Yamaguchi ◽  
R. Frazier ◽  
A. Ho ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Thermal Stability ◽  
Quantum Chemical ◽  
Md Simulations ◽  
Atomic Level ◽  
The Self ◽  
Self Assembled Monolayer ◽  
Thermal Stabilities ◽  
Frictional Forces ◽  
Thermal Stability Of

AbstractTo understand antiwear phenomena in motor engines at the atomic level and provide evidence inselecting future ashless wear inhibitors, we studied the thermal stability of the self-assembled monolayer(SAM) model for dithiophosphate (DTP) and dithiocarbamate (DTC) molecules on the iron oxidesurface using molecular dynamics. The interactions for DTP, DTC and Fe2O3 are evaluated based on aforce field derived from fitting to ab initio quantum chemical calculations of dimethyl DTP (and DTC)and Fe(OH)2(H2O)2-DTP (DTC) clusters. MD simulations at constant-NPT are conducted to assesrelative thermal stabilities of the DTP and DTC with different pendant groups (n-propyl, i-propyl, npentyl.and i-pentyl). To investigate frictional process, we employ a steady state MD method, in whichone of the Fe2O3 slabs maintained at a constant linear velocity. We obtain the time averaged normaland frictional forces from the interatomic forces. Then, we calculated the friction coefficient at theinterface between SAMs of DTP and the confined lubricant, hexadecane, to assess the shear stability ofDTPs with different pendant groups.

scholarly journals A Possible Mechanism of Graphene Oxide to Enhance Thermostability of D-Psicose 3-Epimerase Revealed by Molecular Dynamics Simulations

2021 ◽  
Vol 22 (19) ◽  
pp. 10813
Author(s):  
Congcong Li ◽  
Zhongkui Lu ◽  
Min Wang ◽  
Siao Chen ◽  
Lu Han ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Thermal Stability ◽  
Graphene Oxide ◽  
Md Simulations ◽  
Strong Interactions ◽  
Limiting Factor ◽  
Active Site Residues ◽  
Detailed Mechanism ◽  
Dynamics Simulations ◽  
Thermal Stability Of

Thermal stability is a limiting factor for effective application of D-psicose 3-epimerase (DPEase) enzyme. Recently, it was reported that the thermal stability of DPEase was improved by immobilizing enzymes on graphene oxide (GO) nanoparticles. However, the detailed mechanism is not known. In this study, we investigated interaction details between GO and DPEase by performing molecular dynamics (MD) simulations. The results indicated that the domain (K248 to D268) of DPEase was an important anchor for immobilizing DPEase on GO surface. Moreover, the strong interactions between DPEase and GO can prevent loop α1′-α1 and β4-α4 of DPEase from the drastic fluctuation. Since these two loops contained active site residues, the geometry of the active pocket of the enzyme remained stable at high temperature after the DPEase was immobilized by GO, which facilitated efficient catalytic activity of the enzyme. Our research provided a detailed mechanism for the interaction between GO and DPEase at the nano–biology interface.

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