Second-harmonic generation (SHG) has found extensive applications from hand-held laser pointers to spectroscopic and microscopic techniques. Recently, some cleavable van der Waals (vdW) crystals have shown SHG arising from a single atomic layer, where the SH light elucidated important information such as the grain boundaries and electronic structure in these ultra-thin materials. However, despi...

Double helix variations of glycol nucleic acids (GNA) are revealed by the atomic resolution crystal structure of a 6mer GNA duplex containing solely Watson-Crick type hydrogen-bonded base pairs.

LCAO and PW DFT calculations of the lattice constant, bulk modulus, cohesive energy, charge distribution, band structure, and DOS for UN single crystal are analyzed. It is demonstrated that a choice of the uranium atom relativistic effective core potentials considerably affects the band structure and magnetic structure at low temperatures. All calculations indicate mixed metallic-covalent chemi...

BaBiO3 is a material where formally Bi 4+ ions with the half-filled 6s-states form the alternating set of Bi and Bi ions resulting in a charge ordered insulator. The charge ordering is accompanied by the breathing distortion of the BiO6 octahedra (extension and contraction of the Bi-O bond lengths). Standard Density Functional Theory (DFT) calculations fail to obtain the crystal structure insta...

How does the ordering in a crystal arise from the interactions present? Crystal structure determination shows what the crystal structure is, but in solving directly for atomic coordinates leaves questions as to why (or how) aspects of the structure arise. The answers to such questions are crucial in the study of what drives structural phase transitions or in crystal structure prediction. In thi...

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...

The local and average structure of the Ca endmember of the La1 xCaxMnO3 series has been investigated. Neutron powder diffraction-based high real-space resolution atomic pair distribution function (PDF) analysis, yielding the local atomic structure, and the corresponding Rietveld analysis yielding the average crystal structure show that the two structural scales are in accord in this material, a...

Crystal structures are viewed as being determined by ranges and constraints on interatomic contact distances between neighboring molecules. These distances are considered to arise from environment-dependent atomic sizes, that is, larger sizes for isotropic, van der Waals type contacts and smaller sizes for more-polar, possibly ionic contacts. Although the idea of different, or anisotropic, radi...