This is the preprint of an article that will appear in International Journal of Fracture (IJF)

Title: Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

Abstract:

I am looking for a postdoctoral position. I have expeience in finite element modeling and laboratory measurements of ultrasonic waves in ferroelectric and piezoelectric plates, piezoelectric transducers and actuators, MEMs. Also worked in the field of computational electromagnetics. Please look at the attached resume.

This is the preprint of an article that will appear in Modelling and Simulation in Materials Science and Engineering (MSMSE)

Title: Phase-field simulation of anisotropic crack propagation in ferroelectric single crystals: effect of microstructure on the fracture process

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

Abstract:

I am very interested in a postdoctoral position in computational mechanics, ultrasonics, applied physics, mechanical engineering, or electrical engineering. I am proficient in FEM, FDTD, Moments methods. Experienced in ultrasonic measurements that involve ferroelectric crystals, thin films, periodic structures.  Please see attached resume.

In this letter we obtain the finite-temperature structure
of 180^o domain walls in PbTiO_3 using a quasi-harmonic
lattice dynamics approach. We obtain the temperature dependence of
the atomic structure of domain walls from 0 K up to room
temperature. We also show that both Pb-centered and Ti-centered
180^o domain walls are thicker at room temperature; domain
wall thickness at T=300 K is about three times larger than that of
T=0 K. Our calculations show that Ti-centered domain walls have a
lower free energy than Pb-centered domain walls and hence are more
likely to be seen at finite temperatures.

The electric-field-induced phase transition was investigated under mechanical confinements in bulk samples of an antiferroelectric perovskite oxide at room temperature. Profound impacts of mechanical confinements on the phase transition are observed due to the interplay of ferroelasticity and the volume expansion at the transition. The uniaxial compressive prestress delays while the radial compressive prestress suppresses it. The difference is rationalized with a phenomenological model of the phase transition accounting for the mechanical confinement.

In this paper, we study the effect of normal and shear strains and
oxygen vacancies on the structure of 180^o ferroelectric
domain walls in PbTiO_3.

  The difference to the common model used is the f,g terms. The 3D FEM formulation has been derived and a new fortran program is written. The derivative matrix is symmetric. But the calculation result does not converge. I have tried every means to get a converging result. But it doesn't work, the residual norm always increases.