Kinetic pathways leading to layer-by-layer growth from hyperthermal atoms: A multibillion time step molecular dynamics study

2007 ◽  
Vol 76 (11) ◽  
Author(s):  
D. Adamović ◽  
V. Chirita ◽  
E. P. Münger ◽  
L. Hultman ◽  
J. E. Greene
Keyword(s):  
Molecular Dynamics ◽  
Layer Growth ◽  
Layer By Layer ◽  
Time Step

An Investigation of PT/PT (111) Homoepitaxy with Molecular Dynamics Simulation and Static-Energy Calculation.

1993 ◽  
Vol 317 ◽  
Author(s):  
Ruoping wang ◽  
Bryan S. Kalp ◽  
Kristen A. Fichthorn
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Film Growth ◽  
Effective Medium Theory ◽  
Layer Growth ◽  
Dynamics Simulation ◽  
Energy Calculation ◽  
Layer By Layer ◽  
Static Energy ◽  
Step Edges

ABSTRACTWe present the results of a study of Pt/Pt (111) epitaxial thin-film growth with Molecular-dynamics simulation and static-energy calculation. Interatomic forces are modeled with Corrected-Effective-Medium theory. Atomic details of deposition, such as dissipation of the kinetic energy of an impinging gas atom, adatom motion on and approaching descending step edges, effects of the geometry of a step edge on the interlayer transport of adatoms, etc., have been intensively investigated. We have observed a novel mechanism for adatom incorporation into descending-step edges which involves a concerted motion of the adatom and edge atoms. Our study supports the “island size and shape” model which has been proposed to explain the reentrant layer-by-layer growth mode seen experimentally in Pt/Pt (111) homoepitaxy.

Molecular Dynamics Studies of Semiconductor Thin Films and Interfaces

1987 ◽  
Vol 94 ◽  
Author(s):  
Marcia H. Grabow ◽  
George H. Gilmer
Keyword(s):  
Molecular Dynamics ◽  
Energy State ◽  
Layer Growth ◽  
Metastable Equilibrium ◽  
Free Energy Barrier ◽  
Misfit Dislocations ◽  
Layer By Layer ◽  
3 Dimensional ◽  
Smooth Film ◽  
The Stability

ABSTRACTThe structure and stability of thin epitaxial films have been investigated using molecular dynamics computer simulations. One issue of interest is the stability of a smooth film relative to 3-dimensional clusters. The simulation results show that the uniform film is never the lowest energy state for a system with finite misfit. However, the uniform film, produced in a layer-by-layer growth mode, can persist in a metastable state at substantial misfits, e.g. 10% at 1/2 the melting point. This is a result of the large nucleation barrier to the formation of clusters.The second issue is the quality of the interface between the film and the substrate. At equilibrium, the critical thickness for the introduction of misfit dislocations is larger for films on the diamond cubic (100) substrate than on the (111), and differs from predictions based on continuum mechanics. We find that coherent films remain in metastable equilibrium far beyond the critical misfit calculated for full equilibrium, because a large free energy barrier inhibits the introduction of misfit dislocations.

scholarly journals SIMULATION OF LAYER BY LAYER GROWTH OF FRACTAL METAL Pt-Rh FILMS

2021 ◽  
pp. 682-692
Author(s):  
Дмитрий Викторович Иванов ◽  
Виталий Александрович Анофриев ◽  
Владимир Александрович Кошелев ◽  
Александр Сергеевич Антонов ◽  
Сергей Александрович Васильев ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Image Analysis ◽  
Fractal Dimension ◽  
Tight Binding ◽  
Computer Experiment ◽  
Layer Growth ◽  
Binding Potential ◽  
Layer By Layer ◽  
Fractal Structures ◽  
Continuous Film

В данной работе методом молекулярной динамики с использованием потенциала сильной связи проведено моделирование процесса молекулярно-лучевой эпитаксии с целью определения закономерностей при формировании фрактальных металлических пленок платины на поверхности родия. Установлена возможность формирования фрактальных структур как в островковых пленках платины на поверхности родия, так и в сплошной пленке. Установлены параметры компьютерного эксперимента, определяющие переход от отдельных островковых пленок к сплошной пленке в указанной системе. С использованием различных программных продуктов Gwyddion и Image Analysis, а также собственной разработки FractalSurface проанализирован диапазон изменения фрактальной размерности при различных условиях молекулярно-динамического эксперимента методом подсчета кубов. Полученные значения фрактальной размерности в целом находятся в приемлемом согласии между собой, однако существует ряд исключений, которые обсуждаются более подробно. Сравнительный анализ получаемых результатов позволяет формулировать рекомендации для методики создания, корректировки и прецизионного контроля при «выращивании» структур с заданной морфологией поверхности. In this work, the molecular dynamics method and the tight-binding potential are used to simulate the process of molecular beam epitaxy in order to determine the regularities in the formation of fractal platinum metal films on the rhodium surface. The possibility of formation of fractal structures both in island platinum films on the rhodium surface and in a continuous film has been established. The parameters of the computer experiment, which determine the transition from individual island films to a continuous film in the indicated system, have been established. Using various software products Gwyddion and Image Analysis, as well as our own software FractalSurface, the range of changes in the fractal dimension has been analyzed under various conditions of a molecular dynamics experiment by the method of cube counting. The obtained values of the fractal dimension are generally in acceptable agreement with each other; however, there is a number of exceptions, which are discussed in more detail. A comparative analysis of the results obtained allows one to formulate recommendations for the methodology for creating, adjusting and precision control when «growing» structures with a given surface morphology.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

Oblique-incidence Reflectivity Difference (OI-RD) and Leed Studies of Adsorption and Growth of Xe on Nb(110)

2003 ◽  
Vol 780 ◽  
Author(s):  
P. Thomas ◽  
E. Nabighian ◽  
M.C. Bartelt ◽  
C.Y. Fong ◽  
X.D. Zhu
Keyword(s):  
Transition Layer ◽  
Layer Growth ◽  
Flow Mode ◽  
Layer By Layer ◽  
Zeroth Order ◽  
Step Flow ◽  
Low Energy Electron Diffraction ◽  
Oriented Film ◽  
Low Energy Electron

AbstractWe studied adsorption, growth and desorption of Xe on Nb(110) using an in-situ obliqueincidence reflectivity difference (OI-RD) technique and low energy electron diffraction (LEED) from 32 K to 100 K. The results show that Xe grows a (111)-oriented film after a transition layer is formed on Nb(110). The transition layer consists of three layers. The first two layers are disordered with Xe-Xe separation significantly larger than the bulk value. The third monolayer forms a close packed (111) structure on top of the tensile-strained double layer and serves as a template for subsequent homoepitaxy. The adsorption of the first and the second layers are zeroth order with sticking coefficient close to one. Growth of the Xe(111) film on the transition layer proceeds in a step flow mode from 54K to 40K. At 40K, an incomplete layer-by-layer growth is observed while below 35K the growth proceeds in a multilayer mode.

Evolution of Metastable Structures in Bimetallic Catalysts from Microscopy and Machine-Learning Molecular Dynamics

2020 ◽  
Author(s):  
Jin Soo Lim ◽  
Jonathan Vandermause ◽  
Matthijs A. van Spronsen ◽  
Albert Musaelian ◽  
Christopher R. O’Connor ◽  
...  
Keyword(s):  
Machine Learning ◽  
Molecular Dynamics ◽  
Large Scale ◽  
Materials Science ◽  
Complete Characterization ◽  
Layer By Layer ◽  
Surface Restructuring ◽  
Metastable Structures ◽  
Mechanistic Investigation ◽  
Underlying Mechanisms

Restructuring of interface plays a crucial role in materials science and heterogeneous catalysis. Bimetallic systems, in particular, often adopt very different composition and morphology at surfaces compared to the bulk. For the first time, we reveal a detailed atomistic picture of the long-timescale restructuring of Pd deposited on Ag, using microscopy, spectroscopy, and novel simulation methods. Encapsulation of Pd by Ag always precedes layer-by-layer dissolution of Pd, resulting in significant Ag migration out of the surface and extensive vacancy pits. These metastable structures are of vital catalytic importance, as Ag-encapsulated Pd remains much more accessible to reactants than bulk-dissolved Pd. The underlying mechanisms are uncovered by performing fast and large-scale machine-learning molecular dynamics, followed by our newly developed method for complete characterization of atomic surface restructuring events. Our approach is broadly applicable to other multimetallic systems of interest and enables the previously impractical mechanistic investigation of restructuring dynamics.

scholarly journals A Review on Combination of Ab Initio Molecular Dynamics and NMR Parameters Calculations

2021 ◽  
Vol 22 (9) ◽  
pp. 4378
Author(s):  
Anna Helena Mazurek ◽  
Łukasz Szeleszczuk ◽  
Dariusz Maciej Pisklak
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Small Amplitude ◽  
Ab Initio Molecular Dynamics ◽  
Quantum Mechanical ◽  
Time Step ◽  
Noticeable Effect ◽  
Nmr Parameters ◽  
Mechanical Methods ◽  
Simulation Time

This review focuses on a combination of ab initio molecular dynamics (aiMD) and NMR parameters calculations using quantum mechanical methods. The advantages of such an approach in comparison to the commonly applied computations for the structures optimized at 0 K are presented. This article was designed as a convenient overview of the applied parameters such as the aiMD type, DFT functional, time step, or total simulation time, as well as examples of previously studied systems. From the analysis of the published works describing the applications of such combinations, it was concluded that including fast, small-amplitude motions through aiMD has a noticeable effect on the accuracy of NMR parameters calculations.

scholarly journals Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1631
Author(s):  
Qiang Zhang ◽  
Yohanes Pramudya ◽  
Wolfgang Wenzel ◽  
Christof Wöll
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Deposition Rate ◽  
Layer Growth ◽  
Coarse Grained ◽  
Structural Defects ◽  
Effect Of Temperature ◽  
Layer By Layer ◽  
Reactant Concentration ◽  
Metal Organic

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.

Direct Layer-by-Layer Growth of Crystalline Ag-TCNQ Thin Films on Functionalized Au Substrate: How Critical Is the pH of Ag(I) Solution?

2020 ◽  
Vol 11 (24) ◽  
pp. 10548-10551
Author(s):  
Aswani Sathish Lathika ◽  
Shammi Rana ◽  
Anupam Prasoon ◽  
Pooja Sindhu ◽  
Debashree Roy ◽  
...  
Keyword(s):  
Thin Films ◽  
Layer Growth ◽  
Layer By Layer

High-Quality AlN by Initial Layer-by-Layer Growth on Surface-Controlled 4H-SiC(0001) Substrate

2003 ◽  
Vol 42 (Part 2, No. 5A) ◽  
pp. L445-L447 ◽  
Author(s):  
Norio Onojima ◽  
Jun Suda ◽  
Hiroyuki Matsunami
Keyword(s):  
Layer Growth ◽  
Layer By Layer ◽  
High Quality ◽  
Initial Layer
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