First-principles investigation of the alloying effect of refractory elements Ta and W in the misfit dislocation core of (001) interface

2005 ◽  
Vol 358 (1-4) ◽  
pp. 314-322 ◽  
Author(s):  
C.Y. Geng ◽  
C.Y. Wang ◽  
T. Yu
Keyword(s):  
Misfit Dislocation ◽  
First Principles ◽  
Dislocation Core ◽  
Alloying Effect ◽  
Refractory Elements

Diffusion and Interaction of W and Re in Fe-Cr Alloys

2006 ◽  
Vol 258-260 ◽  
pp. 231-236 ◽  
Author(s):  
Yoshinori Murata ◽  
Tomonori Kunieda ◽  
Kouji Yamashita ◽  
Toshiyuki Koyama ◽  
Effendi ◽  
...  
Keyword(s):  
Ternary System ◽  
Base Alloy ◽  
Ternary Alloys ◽  
Ferritic Steels ◽  
Microstructural Stability ◽  
Alloying Effect ◽  
Refractory Elements ◽  
Basic Understanding ◽  
Heat Resistant Steels ◽  
Interdiffusion Coefficients

The diffusivity of refractory elements in heat resistant steels is crucial for the basic understanding of the microstructural stability during creep. The purposes of this study are to estimate the diffusivity in Fe-Cr alloys as a base alloy for the bcc matrix phase in high Cr ferritic steels and also to investigate the alloying effect of Re on the W diffusivity in them. Fe-15Cr and Fe-20Cr binary alloys, Fe-15Cr-5Re, Fe-15Cr-5W, Fe-20Cr-5Re ternary alloys [mol%] were used in this study. On the basis of the modified ternary Boltzmann-Matano method, the interdiffusion coefficients were obtained in Fe-Cr-Re ternary system. The apparent interdiffusion coefficient for the Re-doped Fe-Cr-W alloy was about one fifth of that for the Re-free alloy. It is concluded that the existence of Re retarded significantly the W diffusion in Fe-15mol%Cr based alloy. This is probably the main reason why a small amount of Re addition suppress the microstructural evolution of W containing high Cr ferritic steels.

scholarly journals First-Principles Calculations of Oxygen-Dislocation Interaction in Magnesium

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 116
Author(s):  
Chao Fang ◽  
Jing Zhang ◽  
Ying Huang ◽  
Jianhao Chen
Keyword(s):  
Screw Dislocation ◽  
First Principles ◽  
Dislocation Core ◽  
Prismatic Slip ◽  
Interstitial Oxygen ◽  
First Principles Calculations ◽  
Dislocation Interaction ◽  
Dislocation Glide ◽  
Deformation Behaviors ◽  
Oxygen Atoms

The interaction between interstitial oxygen atoms and <a>-type screw dislocations was investigated via first-principles calculations to elucidate the effect of oxygen solutes on the deformation behaviors of Mg. The results show that repulsive interactions exist between basal screw dislocation cores and oxygen atoms, which would enable the full basal dislocation to bypass the oxygen atoms in the dislocation glide plane through the cross-slip process. This repulsion also increases the resistance to the motion of dissociated basal dislocations. Moreover, the energy of prismatic <a>-type screw dislocation cores is reduced by the presence of oxygen, which would stabilize the screw dislocation core on the prismatic plane, accordingly facilitating the prismatic slip. This information can complement the fundamental knowledge of alloying Mg using interstitial solutes.

First Principles Simulations of SiC-Based Interfaces

2005 ◽  
Vol 483-485 ◽  
pp. 541-546 ◽  
Author(s):  
A. Catellani ◽  
G. Cicero ◽  
M.C. Righi ◽  
C.A. Pignedoli
Keyword(s):  
First Principles ◽  
Dislocation Core ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Local Geometry ◽  
Microscopic Description ◽  
Semiconductor Interface ◽  
The One ◽  
Solid Liquid Interface ◽  
Solid Liquid

We review some recent investigations on prototypical SiC-based interfaces, as obtained from first-principles molecular dynamics. We discuss the interface with vacuum, and the role played by surface reconstruction in SiC homoepitaxy, and adatom diffusion. Then we move to the description of a buried, highly mismatched semiconductor interface, the one which occurs between SiC and Si, its natural substrate for growth: in this case, the mechanism governing the creation of a network of dislocations at the SiC/Si interface is presented, along with a microscopic description of the dislocation core. Finally, we describe a template solid/liquid interface, water on SiC: based on the predicted structure of SiC surfaces covered with water molecules, we propose (i) a way of nanopatterning cubic SiC(001) for the attachment of biomolecules and (ii) experiments to reveal the local geometry of adsorbed water.

First-principles study of the dislocation core structures on basal plane in magnesium

2014 ◽  
Vol 45 ◽  
pp. 1-7 ◽  
Author(s):  
Tou-Wen Fan ◽  
Quan Zhang ◽  
Li Ma ◽  
Ping-Ying Tang ◽  
Bi-Yu Tang ◽  
...  
Keyword(s):  
First Principles ◽  
Basal Plane ◽  
Dislocation Core ◽  
First Principles Study

Alloying Effect Study on Thermodynamic Stability of MgH2by First-principles Calculation

2016 ◽  
Vol 29 (5) ◽  
pp. 545-548 ◽  
Author(s):  
Zhen-zhen Wan ◽  
Zhong-min Wang ◽  
Dian-hui Wang ◽  
Yan Zhong ◽  
Jian-qiu Deng ◽  
...  
Keyword(s):  
Thermodynamic Stability ◽  
First Principles ◽  
Effect Study ◽  
First Principles Calculation ◽  
Alloying Effect

Fundamentals of Atomistic Simulations

2006 ◽  
Author(s):  
Vasily Bulatov ◽  
Wei Cai
Keyword(s):  
First Principles ◽  
Large Scale ◽  
Dislocation Core ◽  
Boltzmann Distribution ◽  
Atomistic Simulations ◽  
Computationally Efficient ◽  
Interacting Electrons ◽  
Subsequent Discussion ◽  
Necessary And Sufficient ◽  
Interacting Atoms

Fundamentally, materials derive their properties from the interaction between their constituent atoms. These basic interactions make the atoms assemble in a particular crystalline structure. The same interactions also define how the atoms prefer to arrange themselves in the dislocation core. Therefore, to understand the behavior of dislocations, it is necessary and sufficient to study the collective behavior of atoms in crystals populated by dislocations. This chapter introduces the basic methodology of atomistic simulations that will be applied to the studies of dislocations in the following chapters. Section 1 discusses the nature of interatomic interactions and introduces empirical models that describe these interactions with various degrees of accuracy. Section 2 introduces the significance of the Boltzmann distribution that describes statistical properties of a collection of interacting atoms in thermal equilibrium. This section sets the stage for a subsequent discussion of basic computational methods to be used throughout this book. Section 3 covers the methods for energy minimization. Sections 4 and 5 give a concise introduction to Monte Carlo and molecular dynamics methods. When put close together, atoms interact by exerting forces on each other. Depending on the atomic species, some interatomic interactions are relatively easy to describe, while others can be very complicated. This variability stems from the quantum mechanical motion and interaction of electrons [15, 16]. Henceforth, rigorous treatment of interatomic interactions should be based on a solution of Schrödinger’s equation for interacting electrons, which is usually referred to as the first principles or ab initio theory. Numerical calculations based on first principles are computationally very expensive and can only deal with a relatively small number of atoms. In the context of dislocation modelling, relevant behaviors often involve many thousands of atoms and can only be approached using much less sophisticated but more computationally efficient models. Even though we do not use it in this book, it is useful to bear in mind that the first principles theory provides a useful starting point for constructing approximate but efficient models that are needed to study large-scale problems involving many atoms.

scholarly journals Dislocation Core Energies and Core Fields from First Principles

2009 ◽  
Vol 102 (5) ◽  
Author(s):  
Emmanuel Clouet ◽  
Lisa Ventelon ◽  
F. Willaime
Keyword(s):  
First Principles ◽  
Dislocation Core
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