Crystal Growth and Dislocations by A. R. Verma

Crystal Dislocations

Crystal dislocations were invisible until the mid-20th century although their presence had been inferred; the atomic and molecular scale dimensions had prevented earlier discovery. Now they are normally known to be just about everywhere, for example, in the softest molecularly-bonded crystals as well as within the hardest covalently-bonded diamonds. The advent of advanced techniques of atomic-s...

Optical vortices generated by dislocations in a cholesteric liquid crystal.

We report the observation of optical vortices in a laser beam propagating through the stripe pattern of a cholesteric liquid crystal. The liquid crystal is confined in a cell with homogeneous boundary conditions and forms a diffraction phase grating. Optical vortices are produced by edge dislocations of the cholesteric grating. The vortices show up as spots of zero light intensity in the diffra...

Twisted topological solitons and dislocations in a polymer crystal

Charge-density wave phase-slip in niobium triselenide : dislocations and the growth of an, electronic crystal

The analogy is explored between phase-slip in charge-density wave conductors, which brings about the growth and decay of an electronic crystal, and the processes of growth and plastic flow which occur in conventional crystals. The experimental data on NbSq are re-examined, and new measurements of the voltage Vps needed to produce phase-slip at a given rate presented. It is suggested that Vps is...

Screw dislocations in complex, low symmetry oxides: core structures, energetics, and impact on crystal growth.

Determining the atomic structure and the influence of defects on properties of low symmetry oxides have long been an engineering pursuit. Here, we focus on five thermodynamically reversible monoclinic and orthorhombic polymorphs of dicalcium silicates (Ca2SiO3)-a key cement constituent-as a model system and use atomistic simulations to unravel the interplay between the screw dislocation core en...