Molecular dynamics study on the nature of ferroelasticity and piezoconductivity of lanthanum cobaltite

Lanthanum cobaltite systems are known to exhibit unique characteristics under mechanical stress such as ferroelasticity and piezoelasticity. In the present study, molecular dynamics simulation on LaCoO3 was performed to investigate the nature of these characteristics. Under uniaxial compression, the material can accommodate the highest stress in the <111>c direction, i.e., hexagonal c-axis, and this orientation preference is related to displacement of oxygen-ions due to rhombohedrally-distorted CoO6 octahedron. The elastic deformation before ferroelastic domain switching process, where domains are re-oriented to make the hexagonal c-axis parallel to the stress axis, could be attributed to a change in the CoO bond length, whereas the elastic deformation after the switching process could be mostly due to the tilt of CoO6 octahedron. The general lattice deformation (CoCo) proceeds continuously during the whole deformation process. The CoOCo bond angle shows a linear correlation to stress, which could be related to the piezoconductivity.