Adhesion In NiAl-Cr From First Principles

1995 ◽  
Vol 409 ◽  
Author(s):  
James E. Raynolds ◽  
John R. Smith ◽  
David J. Srolovitz ◽  
G.-L. Zhao
Keyword(s):  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Interfacial Stress ◽  
Work Of Adhesion ◽  
Separation Curve ◽  
Self Consistent

AbstractWe have calculated the work of adhesion (i.e. energy for rigid fracture) and peak interfacial stress for NiAl, Cr, and NiAl–Cr using self-consistent density functional calculations to obtain the complete energy vs. separation curve for each system. Our calculations indicate that the work of adhesion is largest for Cr and smallest for NiAI while those for interfaces of NiAI with Cr are intermediate. We have also estimated that segregation processes could alter the work of adhesion for the AlNi/Cr interface by up to 20% since Al tends to segregate to the free NiAl surface while Ni tends to segregate to the AlNi/Cr interface.

scholarly journals Study of odd–even effects in physisorption and chemisorption of Ar, N2, O2 and NO on open shell Ag11–13+ clusters by means of self-consistent van der Waals density functional calculations

2019 ◽  
Vol 21 (45) ◽  
pp. 25158-25174
Author(s):  
Eva M. Fernández ◽  
Luis C. Balbás
Keyword(s):  
Small Molecules ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Van Der Waals ◽  
Open Shell ◽  
Self Consistent

Electronic and structural odd-even effects in the adsorption of small molecules on open shell silver cationic clusters have been rationalized.

First Principles Calculations for Metal/Ceramic Interfaces

1994 ◽  
Vol 357 ◽  
Author(s):  
M. W. Finnis ◽  
C. Kruse ◽  
U. SchÖnberger
Keyword(s):  
Electronic Structure ◽  
High Resolution ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Work Of Adhesion ◽  
First Principles Calculations ◽  
Resolution Electron ◽  
Metal Ceramic

AbstractWe discuss the recent first principles calculations of the properties of interfaces between metals and oxides. This type of calculation is parameter-free, and exploits the density functional theory in the local density approximation to obtain the electronic structure of the system. At the same time the equilibrium atomic structure is sought, which minimises the excess energy of the interface. Up to now calculations of this type have been made for a few model interfaces which are atomically coherent, that is with commensurate lattices. Examples are Ag/MgO and Nb/Al2O3. In these cases it has been possible to predict the structures observed by high resolution electron microscopy. The calculations are actually made in a supercell geometry, in which there are alternating nanolayers of metal and ceramic. Because of the effectiveness of metallic screening in particular, the interfaces between the nanolayers do not interfere much with each other.Besides the electronic structure of the interface, such calculations have provided values of the ideal work of adhesion. Electrostatic image forces in conjunction with the elementary ionic model provide a simple framework for understanding the results.An important role of such calculations is to develop intuition about the nature of the bonding, including the effects of charge transfer, which has formerly only been described in an empirical way. It may then be possible to build atomistic models of the metal/ceramic interaction which have a sound physical basis and can be calibrated against ab initio results. Simpler models are necessary if larger systems, including misfit dislocations and other defects, are to be simulated, with a view to understanding the atomic processes of growth and failure. Another area in which ab initio calculations can be expected to contribute is in the chemistry of impurity segregation and its effect at interfaces. Such theoretical tools are a natural partner to the experimental technique of high resolution electron energy loss spectroscopy for studying the local chemical environment at an interface.

scholarly journals Geometries and Electronic States of Divacancy Defect in Finite-Size Hexagonal Graphene Flakes

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Lili Liu ◽  
Shimou Chen
Keyword(s):  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
Singlet State ◽  
Tight Binding ◽  
Finite Size ◽  
Electronic States ◽  
Closed Shell ◽  
Graphene Flakes ◽  
Self Consistent

The geometries and electronic properties of divacancies with two kinds of structures were investigated by the first-principles (U) B3LYP/STO-3G and self-consistent-charge density-functional tight-binding (SCC-DFTB) method. Different from the reported understanding of these properties of divacancy in graphene and carbon nanotubes, it was found that the ground state of the divacancy with 585 configurations is closed shell singlet state and much more stable than the 555777 configurations in the smaller graphene flakes, which is preferred to triplet state. But when the sizes of the graphene become larger, the 555777 defects will be more stable. In addition, the spin density properties of the both configurations are studied in this paper.

Electric Field Gradient Calculations of Various Borides

1996 ◽  
Vol 51 (5-6) ◽  
pp. 527-533 ◽  
Author(s):  
K. Schwarz ◽  
H. Ripplinger ◽  
P. Blaha
Keyword(s):  
Electric Field ◽  
First Principles ◽  
Density Functional ◽  
The Self ◽  
Full Potential ◽  
Electric Field Gradients ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
Field Gradients ◽  
Self Consistent

Abstract A first-principles method for the computation of electric field gradients (EFG) is illustrated for various borides. It is based on energy band calculations using the full-potential linearized aug-mented plane wave (LAPW) method within density functional theory. From the self-consistent charge density distribution the EFG is obtained without further approximations by numerically solving Poisson's equation. The dependence of the EFG on structure, chemical composition or substitution is demonstrated for the diborides MB2 (with M = Ti, V, Cr, Zr, Nb, Mo, and Ta), the hexaborides (CaB6, SrB6 and BaB6) and boron carbide which is closely related to α-boron.

The Studies of ScB2 (0001) Surfaces from the First-Principles

2014 ◽  
Vol 989-994 ◽  
pp. 688-693
Author(s):  
Hui Zhao ◽  
Qian Han
Keyword(s):  
Energy Density ◽  
Total Energy ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Surface Structures ◽  
Charge Accumulation ◽  
Total Energy Density ◽  
Energy Density Functional

We conduct first-principles total-energy density functional calculations to study the ScB2 (0001) surfaces. The optimized surface structures and electronic properties are obtained. The results show that Sc-terminated surface is thermodynamically more favorable in most of range. The relaxations indicate that it is mainly localized within top three layers and it is less relaxation for Sc-terminated surface. The surface induced features in DOS disappear slowly for the B-terminated surface but vanish rapidly for the Sc-terminated surface. For the Sc-terminated surface, it shows strong metallic property. Simultaneously, both termination surfaces are found charge accumulation relative to the idea surface. Sc-B bonds are strengthened result in the outermost interface spacing are all contracted.

Electronic Structure and Hyperfine Parameters for Hydrogen and Muonium in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
Chris G. Van De Walle
Keyword(s):  
Spin Density ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Hyperfine Parameters ◽  
Bond Center ◽  
Center Site

AbstractFirst-principles spin-density-functional calculations are used to evaluate hyperfine and superhyperfine parameters for hydrogen and muonium at various sites in the Si lattice. The results can be directly compared with values from muon-spin-rotation experiments, leading to an unambiguous identification of “anomalous muonium” with the bond-center site. The agreement found in this case instills confidence in the general use of spin-density-functional calculations for predicting hyperfine parameters of defects.

scholarly journals Native point defects in CuIn1−xGaxSe2: hybrid density functional calculations predict the origin of p- and n-type conductivity

2014 ◽  
Vol 16 (40) ◽  
pp. 22299-22308 ◽  
Author(s):  
J. Bekaert ◽  
R. Saniz ◽  
B. Partoens ◽  
D. Lamoen
Keyword(s):  
Charge Carrier ◽  
Point Defects ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
First Principles Calculations ◽  
Photoluminescence Spectra ◽  
Type Conductivity ◽  
Native Point Defects ◽  
Hybrid Density Functional

Starting from first-principles calculations, many experimental observations such as photoluminescence spectra, charge carrier densities and freeze-out can be explained.

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