A theoretical approach was proposed for testing the validity of isomechanical

analogues for post-perovskite structures. Intrinsic plastic properties were evaluated

for three materials which exhibited a post-perovskite phase: MgSiO3, MgGeO3 and

CaIrO3. The dislocation properties of each structure were determined by using the

Peierls–Nabarro model based upon first-principles calculations of generalised

stacking faults, and the plastic properties were extended to crystal-preferred

orientations using a visco-plastic self-consistent method. This study furnished the

intrinsic parameters of plastic deformation, such as dislocation structures and

Peierls stresses, that could be directly compared between the three materials. It

appeared to be very difficult to draw any simple conclusions concerning

polycrystalline deformation simply by comparing single-crystal properties. In

particular, contrasting the single-crystal properties of MgSiO3 and CaIrO3 led to

similar crystal-preferred orientations of the polycrystal aggregates.

Numerical Modelling of Dislocations and Deformation Mechanisms in CaIrO3 and

MgGeO3 Post-Perovskites—Comparison with MgSiO3 Post-Perovskite. A.Metsue,

P.Carrez, D.Mainprice, P.Cordier: Physics of the Earth and Planetary Interiors,

2009, 174[1-4], 165-73