Symmetry modes provide an alternative method to describe crystal structures. Using the fact that many crystal structures can be described as a distorted version of a higher symmetric parent structure, the traditional atomic positions, occupancies or lattice parameters are no longer used. Instead, all structural features are described applying symmetry modes. This can be of particular interest i...

For two-dimensional (2-D) crystallization we have purified the molecular chaperone GroEL from Escherichia coli to homogeneity. The final and important step for crystallization in the purification procedure was an ATP-agarose column, on which the spacer between ATP and agarose was attached to C8 of adenine. Using the mica spreading "negative staining-carbon film" procedure and polyethylene glyco...

In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice. The spacing between unit cells in various directions is called its lattice parameters. The symmetry properties of the crystal are embodie...

Despite being forbidden in equilibrium, spontaneous breaking of time translation symmetry can occur in periodically driven, Floquet systems with discrete time-translation symmetry. The period of the resulting discrete time crystal is quantized to an integer multiple of the drive period, arising from a combination of collective synchronization and many body localization. Here, we consider a simp...

A twinned crystal is an aggregate in which different domains are joined together according to a specific symmetry operation: the twin law. The diffraction patterns derived from different domains are rotated, reflected or inverted with respect to each other, depending on the nature of the relationship between the different domains, and weighted according to the quantity of a particular domain pr...

We report the results of computer simulations of epitaxial growth in the presence of a large Schwoebel barrier on different crystal surfaces: simple cubic(001), bcc(001), simple hexagonal(001) and hcp(001). We find, that mounds coarse by a step edge diffusion driven process, if adatoms can diffuse relatively far along step edges without being hindered by kink-edge diffusion barriers. This yield...

The structure of catena-poly[[potassium-tri-μ-di-methyl-acetamide-κ(6) O:O] iodide], {[K(C4H9NO)3]I} n , at 120 K has trigonal (P-3) symmetry. The structure adopts a linear chain motif parallel to the crystallographic c axis. Two crystallographically independent K(+) cations are present in the asymmetric unit located on threefold rotoinversion axes at [0, 0, 0] and [0, 0, 1/2] and are bridged b...

The electronic contribution to the magnetically induced polarization in orthorhombic TbMnO3 is studied from first principles. We compare the cases in which the spin cycloid, which induces the electric polarization via the spin-orbit interaction, is in either the b-c or a-b plane. We find that the electronic contribution is negligible in the first case, but much larger, and comparable to the lat...

In single-crystal superconductors in the mixed state, flux-line structures may have a lower symmetry than the host crystal. In this case, multiple degenerate flux lattice domains may be present simultaneously and give rise to complicated small-angle diffraction patterns. The interpretation of these patterns in terms of the flux lattice structure in a single domain is discussed, with particular ...

PATTERN INFORMATION EXTRACTION FROM CRYSTAL STRUCTURES Erhan Okuyan M.S. in Computer Engineering Supervisor: Assist. Prof. Dr. Ug̃ur Güdükbay December, 2005 Determining crystal structure parameters of a material is a quite important issue in crystallography. Knowing the crystal structure parameters helps to understand physical behavior of material. For complex structures, particularly for materi...