Ab initio studium slitiny Ni2MnGa vystavené smykové deformaci

Ab initio study of Ni2MnGa under shear deformation

conference paper

en

The effect of shear deformation on Ni2MnGa magnetic shape memory alloy has been investigated using ab initio electronic structure calculations. We used the projector-augmented wave method for the calculations of total energies and stresses as functions of applied affine shear deformation. The studied nonmodulated martensite (NM) phase exhibits a tetragonally distorted L21 structure with c/a > 1. A large strain corresponding to simple shears in <100>{001}, <001>{100} and <010>{100} systems was applied to describe a full path between two equivalent NM lattices. We also studied <10-1>{101} shear which is related to twining of NM phase. Twin reorientation in this system is possible, because applied positive shear results in path with significantly smaller energetic barrier than for negative shear and for shears in other studied systems. When the full relaxation of lattice parameters is allowed, the barriers further strongly decrease and the structures along the twinning path can be considered as orthorhombic.

Účinek smykové deformace na magnetickou slitinu s tvarovou pamětí Ni2MnGa byl zkoumán s použitím ab initio výpočtů elektronové struktury. Pro výpočet celkové energie a napětí jako funkce aplikované smykové deformace jsme použili metodu projektovaných přidružených vln. Studovaný nonmodulovaný martenzit (NM) vykazuje tetragonálně deformovanou L2_1 strukturu s c/a > 1. Pro popis transformační dráhy mezi dvěma ekvivalentními NM mřížkami byly aplikovány rozsáhlé deformace odpovídající jednoduchému smyku v systémech <100>{001}, <001>{100} a <010>{100}. Také jsme studovali <10-1>{101} smyk, který se vztahuje k dvojčatění NM fáze. Tento smykový systém umožňuje vzájemnou reorientaci dvojčat, protože pozitivní aplikovaný smyk vykazuje dráhu s výrazně menší energetickou bariérou než negativní smyk nebo než v ostatních smykových systémech. Pokud je povolena úplná relaxace mřížkových parametrů, bariéra se dále sníží a struktury podél dráhy dvojčatění mohou být považovány za ortorombické.

The effect of shear deformation on Ni2MnGa magnetic shape memory alloy has been investigated using ab initio electronic structure calculations. We used the projector-augmented wave method for the calculations of total energies and stresses as functions of applied affine shear deformation. The studied nonmodulated martensite (NM) phase exhibits a tetragonally distorted L21 structure with c/a > 1. A large strain corresponding to simple shears in <100>{001}, <001>{100} and <010>{100} systems was applied to describe a full path between two equivalent NM lattices. We also studied <10-1>{101} shear which is related to twining of NM phase. Twin reorientation in this system is possible, because applied positive shear results in path with significantly smaller energetic barrier than for negative shear and for shears in other studied systems. When the full relaxation of lattice parameters is allowed, the barriers further strongly decrease and the structures along the twinning path can be considered as orthorhombic.

Magnetic shape memory alloys; martensitic phase transitions; shear deformation; ab initio calculations;

2015

07.12.2015

EDP Sciences

978-2-7598-1925-6

2261-236X

ESOMAT 2015 – 10th European Symposium on Martensitic Transformations

33

05006-1–05006-6

6