Real-space first-principles electronic structure of edge dislocations: NiAl

Kontsevoi, Oleg Y.; Mryasov, O. N.; Gornostyrev, Yu. N.; Freeman, A. J.; Katsnelson, M. I.; Trefilov, A. V.

doi:10.1080/095008398177832

Cited by 14 publications

(7 citation statements)

References 8 publications

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“…The solid curves show the LDOSs, for the Ti impurity atom in position 8 in the edge dislocation core in ®gure 3 (b) and for the central Ni atom of the core in ®gure 3 (a), labelled with a cross in ®gure 1; these two atoms are nearest neighbours. As we reported previously (Kontsevoi et al 1998b(Kontsevoi et al , 2001, localized electronic states appear on the central Ni atom of the dislocation core, forming a sharp peak of the LDOS near ¡0.33 Ry. From ®gure 3 (b), one can see that the Ti impurity peak turns out to lie lower than its original position, by ¡0.13 Ry; it is shifted to the position of the peak of the localized electronic states on its Ni nearest neighbour, forming a strong resonance with them.…”

supporting

confidence: 79%

“…Later, the possibility of electron localization on some types of dislocation was demonstrated in the framework of the simple singleband TB model (Anokhin et al 1994(Anokhin et al , 1995(Anokhin et al , 1996, and it was suggested that it can lead to radical changes in the energetics of impurity±dislocation interactions. Recently, the formation of localized electronic states on edge dislocations with a h100i Burgers vector in NiAl was con®rmed by ®rst-principles real-space TB linear mu n-tin orbital (LMTO) recursion calculations (Kontsevoi et al 1998b(Kontsevoi et al , 2001. Here we present the results of an ab initio investigation of the interactions of transition-metal impurities with dislocations of this type.…”

mentioning

confidence: 87%

“…The results of our recent ®rst-principles calculations (Kontsevoi et al 1998b(Kontsevoi et al , 2001 demonstrated that localized electronic states exist in the core of h100i edge dislocations in NiAl. Previous calculations for a simpli®ed TB model (Anokhin et al 1994(Anokhin et al , 1995(Anokhin et al , 1996 suggested that localized states may give a signi®cant contribution to the impurity±dislocation interaction.…”

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confidence: 91%

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Electronic mechanism of impurity?dislocation interactions in intermetallics: NiAl

Kontsevoi¹,

Gornostyrev²,

Freeman³

et al. 2001

Philosophical Magazine Letters

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The nature of impurity±dislocation interactions is one of the key questions governing the strength and plasticity of solid-solution materials. To investigate the in¯uence of impurities on the mechanical properties of intermetallic NiAl, the electronic structure and energy of NiAl with a h100if010g edge dislocation and transition-metal impurities was calculated using the real-space tight-binding linear mu n-tin orbital method. The localized electronic states, appearing in the core of the dislocation, are found to lead to strong impurity±dislocation interactions via two mechanisms: ®rstly, chemical locking, due to strong hybridization between impurity electronic states and dislocation localized states; secondly, electrostatic locking, due to long-range charge oscillations caused by the electron localization in the dislocation core. The results obtained explain qualitatively why the solid-solution hardening eOE ect in NiAl correlates with the electronic structure of impurities rather than with size mis®t, as expected according to traditional views.The improvement in the strength of materials by doping with ternary additions has become a traditional alloy design approach. At impurity concentrations below the solubility limit and at su ciently low temperatures where diOE usion processes are suppressed, solid-solution hardening (SSH) (Haasen 1996) is the main reason for an increase in the yield stress y . The value of the SSH, y = c, is determined by the impurity concentration c and their interactions with dislocations. Hence, the nature of elementary impurity±dislocation interactions is one of the key questions in the physics of the strength and plasticity of solid solutions.Although impurity±dislocation interactions depend on many factors, according to the prevailing point of view (Haasen 1996, Suzuki 1979 the size mis®t between the impurity and host atoms,ˆ…1=a †…da=dc †, appears to make the main contribution in the majority of alloys. On the other hand, there is a number of cases, when the electronic structure of impurities play a more important role than size mis®t. In particular, it was found that sp impurities and transition-meta l (d) impurities with the same size mis®t give very diOE erent contributions to SSH in intermetallic Ni 3 Al (Mishima et al. 1986, Abramov andAbramov 1991) (so-called`extra' solution-hard-

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confidence: 79%

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confidence: 87%

mentioning

confidence: 91%

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Electronic mechanism of impurity?dislocation interactions in intermetallics: NiAl

Kontsevoi¹,

Gornostyrev²,

Freeman³

et al. 2001

Philosophical Magazine Letters

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“…The mechanism by which the magnetic field promotes dislocation depinning is mainly free radical energy state conversion. Molotskii [ 22 , 23 ] pointed out that when the distance between the paramagnetic obstacle and the dislocation is less than a nanometre, the interaction between the paramagnetic obstacle and the dislocation will excite free electrons, resulting in the formation of a free radical pair between the paramagnetic obstacle and the dislocation. Free radical pairs can be classified into singlet states (S states) and triplet states (T states) by following the principles of quantum theory.…”

Section: Discussionmentioning

confidence: 99%

Effect of Pulsed Magnetic Field on the Microstructure of QAl9-4 Aluminium Bronze and Its Mechanism

Zhao

Li³

et al. 2022

Materials

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The effect of a pulsed magnetic field on the microstructure of a QAl9-4 aluminium bronze alloy was studied in this work. It was found that the dislocation density, grain boundary angle, and microhardness of the alloy significantly changed after the magnetic field treatment with a peak magnetic induction intensity of 3T, pulse duration of about 100 us, pulse interval of 10 s, and pulse time of 360. EBSD was used to test the KAM maps of the alloy microzone. It was found that the alloy’s dislocation density decreased by 10.88% after the pulsed magnetic field treatment; in particular, the dislocation in the deformed grains decreased significantly. The quantity of dislocation pile-up and the degree of distortion around the dislocation were reduced, which decreased the residual compressive stress on the alloy. Dislocation motion caused LAGB rotation, which reduced the misorientation of adjacent points inside the grain. The magnetic field induced the disappearance of deformation twins and weakened the strengthening effect of twins. The microhardness test results show that the alloy’s microhardness decreased by 8.06% after pulsed magnetic field treatment. The possible reasons for the magnetic field effect on dislocation were briefly discussed. The pulsed magnetic field might have caused the transition to the electronic energy state at the site of dislocation pinning, which led to free movement of the vacancy or impurity atom. The dislocation was easier to depin under the action of internal stress in the alloy, changing the dislocation distribution and alloy microstructure.

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“…The effect of a charged dislocation can be treated in a continuum sense by considering Coulomb scattering from a line of uniform charge density [14]. In semiconductors and intermetallics, broken bonds in the core can give rise to quasilocalized states and various related optical effects [12,15]. Conduction electron scattering by the dislocation strain field has also been presented for semiconductors [16], exactly analogous to the deformation potential calculation in metals.…”

Section: Introductionmentioning

confidence: 99%

Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations

Viswanathan

Chandrasekar

2014

Journal of Applied Physics

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A theory for conduction electron scattering by inhomogeneous crystal lattice strains is developed, based on the differential geometric treatment of deformations in solids. The resulting fully covariant Schrödinger equation shows that the electrons can be described as moving in a non-Euclidean background space in the continuum limit of the deformed lattice. Unlike previous work, the formalism is applicable to cases involving purely elastic strains as well as discrete and continuous distributions of dislocations -in the latter two cases it clearly demarcates the effects of the dislocation strain field and core and differentiates between elastic and plastic strain contributions respectively. The electrical resistivity due to the strain field of edge dislocations is then evaluated using perturbation theory and the Boltzmann transport equation. The resulting numerical estimate for Cu shows good agreement with experimental values, indicating that the electrical resistivity of edge dislocations is not entirely due to the core, contrary to current models. Possible application to the study of strain effects in constrained quantum systems is also discussed.

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Real-space first-principles electronic structure of edge dislocations: NiAl

Cited by 14 publications

References 8 publications

Electronic mechanism of impurity?dislocation interactions in intermetallics: NiAl

Electronic mechanism of impurity?dislocation interactions in intermetallics: NiAl

Effect of Pulsed Magnetic Field on the Microstructure of QAl9-4 Aluminium Bronze and Its Mechanism

Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations

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