On the effect of deformation twins on stability of B19′ structure in NiTi martensite

The present study is focused on discrepancy between theoretically predicted (base centered orthorhombic B33) and experimentally observed (monoclinic B19′) ground state structures of NiTi martensite. In particular, we deal with a hypothesis on possible effect of presence of twins on the martensite structure. Several models of (100) twins in NiTi martensite (representing several twin densities) are studied from first principles. Computational supercells are fully optimized in order to reach almost stress-free state for each twin model. Our results show that the presence of twins has a significant influence on crystal geometry that tends to stabilize B19′ structure rather than the B33 one, at least for higher twin densities.