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Joint Postdoctoral Fellow Position at KAUST and Georgia Institute of Technology

Submitted by arash_yavari on

                                     

Joint Postdoctoral Fellow Position at KAUST and Georgia Institute of Technology — Accepting applications until the position is filled


We have one more opening and have no U.S. visa waiver requirement anymore.

Finite-Temperature Atomic Structure of 180^o Ferroelectric Domain Walls in PbTiO_3

Submitted by arash_yavari on

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

Estimating Terminal Velocity of Rough Cracks

Submitted by arash_yavari on

In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed.

Structure of Defective Crystals at Finite Temperatures: A Quasi-Harmonic Lattice Dynamics Approach

Submitted by arash_yavari on

In this paper we extend the classical method of lattice dynamics to defective crystals with partial symmetries. We start by a nominal defect configuration and first relax it statically. Having the static equilibrium configuration, we use a quasiharmonic lattice dynamics approach to approximate the free energy. Finally, the defect structure at a finite temperature is obtained by minimizing the approximate Helmholtz free energy. For higher temperatures we take the relaxed configuration at a lower temperature as the reference configuration.

Effect of strain and oxygen vacancies on the structure of 180^o ferroelectric domain walls in PbTiO_3

Submitted by arash_yavari on

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.

A Geometric Theory of Thermal Stresses

Submitted by arash_yavari on

In this paper we formulate a geometric theory of thermal stresses.

Given a temperature distribution, we associate a Riemannian

material manifold to the body, with a metric that explicitly

depends on the temperature distribution. A change of temperature

corresponds to a change of the material metric. In this sense, a

temperature change is a concrete example of the so-called

referential evolutions. We also make a concrete connection between

our geometric point of view and the multiplicative decomposition