Atomic structure of the Σ5 (310)/[001] symmetric tilt grain boundary in molybdenum

Campbell, Geoffrey H.; Belak, J.; Moriarty, John A.

doi:10.1016/s1359-6454(99)00258-x

Cited by 40 publications

(18 citation statements)

References 21 publications

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“…The results of the present study on Ta, when combined with previously reported results on Nb [8] and MO [9], reaffirms the predictive power of the MGPT derived potentials for modeling defect structures in the BCC metals.…”

Section: Discussionsupporting

confidence: 89%

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Electronic Effects on Grain Boundary Structure in Bcc Metals

et al. 1999

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The dominant factor in determining the atomic structure of grain boundaries is the crystal structure of the material, e.g. FCC vs. BCC. However, for a given crystal structure, the structure of grain boundaries can be influenced by electronic effects, i.e. by the element comprising the crystal. Understanding and modeling the influence of electronic structure on defect structures is a key ingredient for successful atomistic simulations of materials with more complicated crystal structures than FCC. We have found that grain boundary structure is a critical test for interatomic potentials. To that end, we have fabricated the identical x5 (3 lO)/[OOl] symmetric tilt grain boundary in three different BCC metals (Nb, MO, and Ta) by diffusion bonding precisely oriented single crystals. The structure of these boundaries have been determined by high resolution transmission electron microscopy. The boundaries have been found to have different atomic structures. The structures of these boundaries have been modeled with atomistic simulations using interatomic potentials incorporating angularly dependent interactions, such as those developed within Model Generalized Pseudopotential Theory. The differing structures of these boundaries can be understood in terms of the strength of the angular dependence of the interatomic interaction. We report here the results for Ta. INTRODUCTIONAtomistic simulations are an increasingly important means of understanding the behavior of materials under a variety of conditions. With this technique, an assembly of thousands, or even millions, of atoms is defined in a computer simulation and allowed to interact according to certain rules and boundary conditions. The boundary conditions include temperature and states of stress, allowing the calculation of such properties as the equation of state or unstable stacking fault energy. The structure and properties of crystal defects can also be predicted, such as the stressed configuration of a dislocation core or the interaction energy of an interstitial with a vacancy (see e.g. [l]). The rules of interaction are often very simple in order to speed computation. This simplification requires approximations to be made about the physics of the interacting atoms. Hence, in the development of models of interatomic interactions, an evaluation is necessary of whether the essential physics have been incorporated in the model. The models are tested by comparing their predic'tions with experimental observations.Receqtly developed models of interatomic interactions incorporate angularly dependent contributions to model materials with directional bonding [2-71, such as the body centered cubic transition metals in which the d -bands participate in bonding. The strength of the directional component of the bonding has a major influence on the structure of crystal defects. The model of interatomic interactions with angular dependence that we use is the Model Generalized Psuedopotential Theory (MGPT) [5]. We have applied it to modeling the x5 (3 1 O)/[OO 1 ] symm...

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Section: Discussionsupporting

confidence: 89%

“…The model of interatomic interactions with angular dependence that we use is the Model Generalized Psuedopotential Theory (MGPT) [5]. We have applied it to modeling the x5 (3 1 O)/[OO 1 ] symmetric tilt grain boundary (STGB) in niobium [8], molybdenum [9], and tantalum as a critical test of its accuracy. We report here on the results for Ta.…”

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confidence: 99%

Electronic Effects on Grain Boundary Structure in Bcc Metals

et al. 1999

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“…In previous studies of the structure of a ⌺5͑310͒ GB in Mo, 39 Nb, 40 and Ta, 41 investigated by means of the model generalized pseudopotential theory ͑MGPT͒, a breaking of the mirror symmetry was found for Mo and Ta, but not for Nb. A similar result was obtained also by Ochs et al 42 In MGPT, the interatomic forces are described by pair-and three-body potentials, while our ab initio calculations give the full account of quantum many-body forces.…”

Section: A Structure Of Grain Boundarymentioning

confidence: 89%

First-principles study of magnetism at grain boundaries in iron and nickel

2008

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The geometric and magnetic structures of fully relaxed symmetrical tilt ⌺5͑310͒ grain boundaries ͑GBs͒ in iron and ⌺5͑210͒ GBs in nickel have been investigated using density-functional theory. We found for both GBs an enhancement of the local magnetic moments of atoms in the GB plane ͑2.55 B for iron and 0.67 B for nickel͒ which is correlated with the larger local atomic volume compared to the bulk. At larger distances from the GB the variation of the local magnetic moments follows the changes in the exchange splitting in the spin-polarized local density of states imposed by the local variations in the atomic geometry. When Si and Sn impurity atoms in interstitial or substitutional positions appear at the ⌺5͑310͒ GB in iron, the local magnetic moments of iron atoms are reduced for silicon and almost unchanged for tin. We also calculated the segregation enthalpies of both impurities and confirmed the experimental fact that silicon is a substitutional and tin an interstitial segregant; the calculated values of segregation enthalpy are in good agreement with experiment.

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“…The R5 (3 1 0)/ [0 0 1] Mo STGB can be well presented by atomistic simulations using interatomic potentials based on the model generalized pseudopotential theory (MGPT), and is proved to be a low energy configuration [29]. Experimentally, on the other hand, the R5 (3 1 0)/ [0 0 1] Mo STGB can also be fabricated and characterized by highresolution transmission electron microscopy (HRTEM), in agreement with atomistic simulations [28,29]. Employing the first-principles method, we calculate H dissolution behaviors at both interstitial and vacant sites (vacancies) in a R5 (3 1 0)/[0 0 1] Mo STGB, and further explore the diffusion properties of H among these sites along the Mo GB.…”

Section: Introductionmentioning

confidence: 99%