UNIT-I
Crystal Structure and X-Rays
Crystal Systems and X-rays: Crystal Structure: Space Lattice Translation vectors, Basis of crystal structure, Types of unit cell, Primitive, non primitive cells, seven crystal system, coordination numbers, Miller indices, Expression for inter planner spacing.
X-Rays: Production and properties of X-rays, Coolidge tube, Continuous and characteristic X-ray Spectra, Moseley's law, X-ray diffraction, Scattering of X-Ray's Bragg's X-ray spectrometer- powder diffraction method, Intensity Vs 2tita plot …..Etc.
UNIT CELL
Unit cell-- smallest grouping which can be arranged in three dimensions to create the lattice. Thus the Unit Cell is basic structural unit or building block of the crystal structure
Crystal Systems
• Since there are many different possible crystal structures, it is sometimes convenient to divide them into groups according to unit cell configurations and/or atomic arrangements.
• One such scheme is based on the unit cell geometry, i.e. the shape of the appropriate unit cell parallelepiped without regard to the atomic positions in the cell.
• Within this framework, an x, y, and z coordinate system is established with its origin at one of the unit cell corners; each x, y, and z-axes coincides with one of the three parallelepiped edges that extend from this corner, as illustrated in Figure.
Bragg's Law and Reciprocal Lattice.
• X Rays• X Ray Spectra• X Ray Diffraction and• Bragg's Law• Reciprocal Lattice• Bragg's Law in Reciprocal Space• Ewald Sphere
X-Ray Analysis
• X-rays discovered in 1895
• Fundamental to understanding of crystal structure and symmetry
• Powder diffraction analyses are a simple and inexpensive method for identifying minerals, especially fine-grained minerals
X-ray Crystallograph
X-ray wavelengths are on the same order of magnitude as atomic spacings.
Crystals thus make excellent diffraction gratings
Can use the geometry of the x-ray spots to determine geometry of grating (i.e. the crystal)
… Etc.