scholarly journals THERMODYNAMICS OF TYPE II KEROGEN TRANSFORMATION

2019 ◽  
Vol 3 (180) ◽  
pp. 25-40
Author(s):  
Yuri Khokha ◽  
Oleksandr Lyubchak ◽  
Myroslava Yakovenko
Keyword(s):  
Molecular Dynamics ◽  
Solid Phase ◽  
High Energy ◽  
Type Ii ◽  
Distribution Of Elements ◽  
Gas System ◽  
Hydrocarbon Gas ◽  
Molecular Dynamics Methods ◽  
Transformation Of Organic Matter ◽  
Physical And Chemical

The article reviews the chemical structure of type II kerogen. The changes that occur with the structure of type II kerogen as it passes through the stages of catagenesis from immature to post-mature are evaluated. Structural models of type II kerogen at different stages of catagenesis are presented: both obtained empirically after studying the structure by physical and chemical methods and the results of modelling by molecular dynamics method. Methods of equilibrium thermodynamics are used to calculate the composition of the kerogen–gas system for crust sections in the range of 1–20 km with a heat flux of 40 to 100 mW/m2. The composition of kerogen/fluid geochemical system is calculated using the E. T. Jaynes formalism. It boils down to determining the optimal distribution of 5 elements (C, H, O, N, S) among the 44 additive constituents of the solid phase (i. e., type II kerogen) and other individual components that are included in the system (CO2, H2O, H2S, NH3, CH4, C2H6, C3H8, i-C4H10, n-C4H10, i-C5H12, neo-C5H12, n-C5H12). Comparison with the experiments showed that the results of the calculations do not contradict the experiments, with study the structure and changes in type II kerogen with increasing degree of catagenesis. In the analysis of changes in the concentrations of water, carbon dioxide and hydrogen sulfide, it is founded that kerogen could be not only a donor of atoms for gas components, but also their acceptor in contact with a high-energy fluid stream. It is shown that the determination of sulfur-containing atomic groups of kerogen by thermodynamic modelling yields gives more reliable results than molecular dynamics methods. Established is that the concept of “methane-graphite death”, which takes place in the state of thermodynamic equilibrium in the transformation of organic matter, is erroneous. The calculation shows that the composition of the kerogen–gas system, in addition to methane and carbon, includes solid-phase heteroatom groups, various additive components of aromatic structures and gases, both organic and inorganic. The distribution of elements between the additive components of kerogen and gases in this system controls the pressure and temperature in a complex way. The nature of changes in hydrocarbon gas concentrations in equilibrium with type II kerogen indicates the presence of an “oil window” in low-warmed zones within 2–4 km depths.

Determination of surface tension by molecular dynamics methods for monatomic substances

2014 ◽  
Vol 10 ◽  
pp. 73-77
Author(s):  
V.L. Malyshev ◽  
D.F. Maryin ◽  
E.F. Moiseeva ◽  
N.A. Gumerov ◽  
I.Sh. Akhatov
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Surface Tension ◽  
Interaction Potential ◽  
Numerical Results ◽  
Molecular Dynamics Method ◽  
Gas System ◽  
Molecular Dynamics Methods ◽  
Dynamics Method

The results of the calculation of surface tension by the molecular dynamics method for the liquid-gas system based on the example of argon are presented in the article. The method was verified by comparing numerical results with experimental data. The results on the determination of the optimal trimming radius for the interaction potential are presented.

scholarly journals Development of Continuum-Atomistic Approach for Modeling Metal Irradiation by Heavy Ions

2018 ◽  
Vol 173 ◽  
pp. 03005
Author(s):  
Balt Batgerel ◽  
Stefka Dimova ◽  
Igor Puzynin ◽  
Taisia Puzynina ◽  
Ivan Hristov ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Heavy Ions ◽  
High Energy ◽  
Atomistic Model ◽  
Heterogeneous Cluster ◽  
Thermal Spike Model ◽  
Spike Model ◽  
Molecular Dynamics Methods ◽  
Active Research ◽  
Labor Consuming

Over the last several decades active research in the field of materials irradiation by high-energy heavy ions has been worked out. The experiments in this area are labor-consuming and expensive. Therefore the improvement of the existing mathematical models and the development of new ones based on the experimental data of interaction of high-energy heavy ions with materials are of interest. Presently, two approaches are used for studying these processes: a thermal spike model and molecular dynamics methods. The combination of these two approaches – the continuous-atomistic model – will give the opportunity to investigate more thoroughly the processes of irradiation of materials by high-energy heavy ions. To solve the equations of the continuous-atomistic model, a software package was developed and the block of molecular dynamics software was tested on the heterogeneous cluster HybriLIT.

Formation and dissociation of shear-induced high-energy dislocations: insight from molecular dynamics simulations

2021 ◽  
Author(s):  
Nanjun Chen ◽  
Shenyang HU ◽  
Wahyu Setyawan ◽  
Bharat Gwalani ◽  
Peter Sushko ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Large Scale ◽  
Solid Phase ◽  
High Energy ◽  
Surface Characteristic ◽  
Geometric Constraints ◽  
Tribological Tests ◽  
Inhomogeneous Strain ◽  
Dynamics Simulations

Abstract Solid-phase processing (SPP) allows one to create complex microstructures, not achievable via thermal processing alone. The resulting structures exhibit a rich palette of defects, both thermal and non-thermal, including defect substructures, such as dislocation networks. It is essential to understand the mechanisms of deformation and defect structure formation to guide SPP towards achieving desired microstructures and material properties. In this study, large-scale molecular dynamics simulations are used to investigate the effects of inhomogeneous strain distribution, that mimics deformation conditions of tribological tests, on the evolution of defects under severe shear deformation in polycrystalline Al. Analysis of defect nucleation and reaction pathways reveals that strong geometric constraints suppress the nucleation and slide of low energy dislocation 1/2<110>{111} but promote the nucleation and slide of high energy dislocations, such as [1-10](001) and 1/2[1-1-2](1-11). A rough contact surface, characteristic to tribological tests, imposes an inhomogeneous stress field leading to inhomogeneous defect substructures due to location-dependent activation of slip systems. The results suggest that high-energy dislocations can dominate the evolution of grain structures in highly constrained environments, which should be considered in modeling plastic deformation and grain refinement during SPP.

Molecular-dynamics studies on solid phase epitaxy of guest-free silicon clathrates

2001 ◽  
Vol 691 ◽  
Author(s):  
Shinji Munetoh ◽  
Koji Moriguchi ◽  
Teruaki Motooka ◽  
Kazuhito Kamei
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Structural Transition ◽  
Solid Phase ◽  
Experimental Studies ◽  
Md Simulations ◽  
Type I ◽  
Solid Phase Epitaxy ◽  
Type Ii ◽  
Silicon Clathrates

ABSTRACTDynamical phenomena during the solid phase epitaxy (SPE) of guest-free Si clathrates (Si34 and Si46) via molecular-dynamics (MD) simulations using the Tersoff potential have been reported. The activation energy of SPE for Si34 has been found to correspond with the experimental value for the cubic diamond phase (c-Si; approximately 2.7eV), while the SPE rates of Si46 are much lower than that of c-Si. The structural transition from Si46 (type-I) to Si34 (type-II) can be also observed during the Si46 [001] SPE. The present results suggest that it is worthwhile to intensify experimental studies concerning crystal growth techniques of clathrate materials and these interesting Si forms may open up a new field in “silicon technologies”.

scholarly journals Simulation of Formation of Icosahedral Structure in Solid-Liquid-Solid Phase Change Using Molecular Dynamics Methods

2017 ◽  
Vol 17 (1) ◽  
pp. 19 ◽  
Author(s):  
Nikodemus Umbu Janga Hauwali ◽  
Artoto Arkundato ◽  
Lutfi Rohman
Keyword(s):  
Molecular Dynamics ◽  
Phase Change ◽  
Solid Phase ◽  
Icosahedral Phase ◽  
Temperature Decrease ◽  
Icosahedral Structure ◽  
Cooling Temperature ◽  
Molecular Dynamics Methods ◽  
Phase Liquid ◽  
Solid Liquid

It has successfully conducted research to study the structure of the icosahedral formation in the event of change of the solid phase - liquid-solid using molecular dynamics method . The result showed that the percentage of the maximum icosahedral structure is obtained when the simulation is run at the start of the cooling temperature of 2875 K at a rate of temperature decrease of 0.064 K /step and at the beginning of the cooling temperature of 3000 K at a rate of temperature decrease 0.12 K/step. While icosahedral minimum percentage obtained when the simulation is run at a temperature of 2750 K with the initial cooling rate of temperature decrease of 0.069 K/step. Based on these results we can conclude that there is a relationship between the initial temperature of the cooling and the rate of temperature decrease of the icosahedral structure is formed. Keywords: Icosahedral, phase change, molecular dynamics

scholarly journals Hydrogen Inter-Cage Hopping and Cage Occupancies inside Hydrogen Hydrate: Molecular-Dynamics Analysis

2020 ◽  
Vol 11 (1) ◽  
pp. 282
Author(s):  
Yogeshwaran Krishnan ◽  
Mohammad Reza Ghaani ◽  
Arnaud Desmedt ◽  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Energy Barrier ◽  
Guest Molecule ◽  
Arrhenius Equation ◽  
Dynamics Simulation ◽  
Type Ii ◽  
Large Cage ◽  
Guest Molecules ◽  
Simulation Time ◽  
Average Occupancy

The inter-cage hopping in a type II clathrate hydrate with different numbers of H2 and D2 molecules, from 1 to 4 molecules per large cage, was studied using a classical molecular dynamics simulation at temperatures of 80 to 240 K. We present the results for the diffusion of these guest molecules (H2 or D2) at all of the different occupations and temperatures, and we also calculated the activation energy as the energy barrier for the diffusion using the Arrhenius equation. The average occupancy number over the simulation time showed that the structures with double and triple large-cage H2 occupancy appeared to be the most stable, while the small cages remained with only one guest molecule. A Markov model was also calculated based on the number of transitions between the different cage types.

scholarly journals Physicochemical Characteristics of Arginine Enriched NaF Varnish: An In Vitro Study

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2998
Author(s):  
Mohammed Nadeem Bijle ◽  
Manikandan Ekambaram ◽  
Edward Lo ◽  
Cynthia Yiu
Keyword(s):  
Molecular Dynamics ◽  
Physical Properties ◽  
Artificial Saliva ◽  
Chemical Properties ◽  
In Vitro Study ◽  
Physicochemical Characteristics ◽  
Vitro Study ◽  
Physical And Chemical ◽  
Stable Matrix

The in vitro study objectives were to investigate the effect of arginine (Arg) incorporation in a 5% sodium fluoride (NaF) varnish on its physical and chemical properties including F/Arg release. Six experimental formulations were prepared with L-arginine (L-Arg) and L-arginine monohydrochloride at 2%, 4%, and 8% w/v in a 5% NaF varnish, which served as a control. The varnishes were subjected to assessments for adhesion, viscosity, and NaF extraction. Molecular dynamics were simulated to identify post-dynamics total energy for NaF=Arg/Arg>NaF/Arg<NaF concentrations. The Arg/F varnish release profiles were determined in polyacrylic lactate buffer (pH-4.5; 7 days) and artificial saliva (pH-7; 1 h, 24 h, and 12 weeks). Incorporation of L-Arg in NaF varnish significantly influences physical properties ameliorating retention (p < 0.001). L-Arg in NaF varnish institutes the Arg-F complex. Molecular dynamics suggests that NaF>Arg concentration denotes the stabilized environment compared to NaF<Arg (p < 0.001). The 2% Arg-NaF exhibits periodic perennial Arg/F release and shows significantly higher integrated mean F release than NaF (p < 0.001). Incorporating 2% L-arginine in 5% NaF varnish improves its physical properties and renders a stable matrix with enduring higher F/Arg release than control.

Proton spin thermometry and molecular dynamics of the liquid crystal PAA in the solid phase

1974 ◽  
Vol 61 (11) ◽  
pp. 4646-4649 ◽  
Author(s):  
R. T. Thompson ◽  
D. W. Kydon ◽  
M. M. Pintar
Keyword(s):  
Molecular Dynamics ◽  
Liquid Crystal ◽  
Solid Phase ◽  
Proton Spin
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