User:Anjali Merin/sandbox

= Crystallography and Mineral Evolution = Crystallography is the science that examines crystals, which can be found everywhere in nature—from salt to snowflakes to gemstones. It uses the properties and inner structures of crystals to determine the arrangement of atoms and generate knowledge that is used by chemists, physicists, biologists, and others. Within the past century, crystallography has been a primary force in driving major advances in the detailed understanding of materials, synthetic chemistry, the understanding of basic principles of biological processes, genetics, and has contributed to major advances in the development of drugs for numerous diseases. It is one of the most important tool to study solids, since most of the materials in solid state exhibits crystalline nature. Crystalline solids are known to show different structural forms depending on different conditions of temperature, pressure etc. Since minerals are naturally occurring inorganic crystalline, the phase transitions involving minerals will be interesting. Phase transition studies of minerals deserve special attention as they can provide clues to mechanism of mineral evolution on earth crust. They also opens up the possibility of utilizing the naturally abundant minerals for generating novel functional materials processing properties such as ionic conductivity, ferroelecticity, ferromagnetism etc.

A mineral  is  an  element  or  chemical  compound  that  is  normally crystalline and that has been formed as a result of geological process. It has highly ordered atomic structure and specific physical properties. Mimicking the mineral evolution process in laboratory by phase transition studies can throw lights on our understanding of mineral evolution. A large number of minerals occur in hydrated form, especially the bimetallic sulfate minerals are widely interested in its varying non stoichiometric crystal structure with the levels of hydration. Bimetallic sulfates are more interested due to their phase transition with temperature, eg; langbenites, krohnkite. The non-stoichiometric structures getting trapped in small kinetically stabilized energy wells, which are intermediates between individual monosulfates and bimetallic sulfate minerals, may have valuable structural hints about the process of origin of such minerals. The phase transition studies reveal that those structures are precursors of the original mineral and the ubiquitous role of water in the formation of minerals in the earth crust.

In particular, Langebenite  minerals  are  distinctive  geological  minerals found  in only  a  few  locations  in  the  world. These deposits were formed millions of years ago when a variety of salts were left behind after the evaporation of ancient ocean beds. These type crystals have general chemical formulae A2B2(SO4)3 where A denotes a monovalent cation such as K, NH4… and B a divalent cation such as Mg, Mn, Ni… At high temperatures, they crystallizes isomorphously in the cubic space group P213. They are having a wide variety of applications due to its ferroelectric, ferroelastic, spectroscopic and magnetic properties [2]. Their best-known applications are in dosimetry of ionizing radiation, CTV screen phosphors, projection T V phosphors, scintillators, fluorescent lamps, full color displays, X-ray storage and screens intensifying phosphors, and laser materials.