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What Types of Stacking Faults and Dislocation Dissociations Can Be Found in Transition-Metal Disilicides

100%

Paidar V., Čák M., Šob M., Inui H.

Acta Physica Polonica A

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2015

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vol. 128

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issue 4

589-591

EN

Identical atomic planes of transition-metal disilicides can form different stacking when they are ordered in several combinations of four different positions A, B, C, D. The following arrangements can be formed: AB in C11_b structure of e.g. MoSi₂, ABC in C40 structure of e.g. VSi₂ and ABDC in C54 structure of e.g. TiSi₂ disilicides. The ABC atomic plane stacking along the ⟨111⟩ cubic directions is well known in the fcc lattice, where three basic types of stacking faults are known: intrinsic or extrinsic faults and elementary twin, however, other types of stacking faults can be detected in transition-metal disilicides due to the occurrence of the fourth position D. On the other hand, the faults well known in metallic systems as antiphase boundaries need not be metastable in disilicides. Based on the results of ab initio calculations, it can be predicted which types of planar defects are metastable corresponding to the local minima on the energy surface of generalized stacking faults or unstable when they are represented, for example, by saddle points. The character of dissociation of the dislocation cores is directly related to the existence of metastable stacking faults. Moreover, the space distribution of dislocation cores has a direct impact on dislocation mobility and, therefore, also on macroscopic mechanical properties of materials. The behaviour of extended crystal defects in disilicides that is caused by covalent interatomic bonding, is discussed starting from the geometrical analysis, and it is demonstrated that predictions of materials properties can be deduced.

2

Preferential Positron Annihilation in Binary Alloys

100%

Kuriplach J., Dryzek E., Dryzek J., Šob M.

Acta Physica Polonica A

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1999

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vol. 95

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issue 4

605-611

EN

The effect of preferential positron annihilation at individual constituent atoms in binary alloys is examined theoretically and experimentally. In particular, the results of recently studied alloys Fe-Al and Mg-Cd together with new preliminary results for the Sn-In system are discussed and summarised. In the case of the Sn-In system, the concentration dependencies of positron annihilation rates and Doppler broadening spectra are analysed.

3

Interlayer Exchange Coupling: Effect of Alloying

88%

Kudrnovský J., Drchal V., Turek I., Šob M., Weinberger P.

Acta Physica Polonica A

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1997

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vol. 91

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issue 1

15-25

EN

The effect of disorder in magnetic layers, in the spacer, and at interfaces between them on periods, amplitudes, and phases of oscillations of interlayer exchange coupling in magnetic multilayers is studied theoretically on the ab initio level. We employ the spin-polarized surface Green function technique within the tight-binding linear muffin-tin orbital method and the Lloyd formulation of the interlayer exchange coupling. The coherent potential approximation is used to describe the effect of alloying. The calculations are significantly simplified by employing the vertex-cancellation theorem. Numerical results illustrating the effect of various kinds of disorder in the system on the properties of the interlayer exchange coupling are presented.

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3 Acta Physica Polonica A

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3 Šob M.

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1 Dryzek E.

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1 Kuriplach J.

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1 Weinberger P.

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What Types of Stacking Faults and Dislocation Dissociations Can Be Found in Transition-Metal Disilicides

Preferential Positron Annihilation in Binary Alloys

Interlayer Exchange Coupling: Effect of Alloying