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چكيده انگليسي :

Determination of Optical Properties of Tungsten Trioxide Clusters and Deviation of Incorporation of Hydrogen on Optical Properties with Time Dependent Density Functional Theory Mohammad Mahdi Davari Esfahani m davari@ph iut ac ir Jan 22 2013 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisor Dr M Alaei m alaei@cc iut ac irAbstractTime Dependent Density Functional Theory as a powerful tool for obtaining optical spectra of diver sity of molecular systems is gaining day to day popularity for the aim of simulation Recently thereis a great concern among scientists on employing this tool for simulation of optical spectra of atomicand molecular systems Since obtained optical spectra of this method has a great agreement with ex perimental result most of developers are encouraged to have this type of calculation in their packages Different studies demonstrated that Tungsten Trioxide shows a great change in its properties in thepresence of the first row elements of periodic table such as Hydrogen Sodium and so forth The mostmomentous change within these various alteration is optical properties In accordance with its greatusage in industry it is an on the table subject that has been used in making smart windows windowswith changeable transparency mirrors with changeable reflection and so forth In this study first the most stable structures of tungsten trioxide clusters have been obtained bychecking the relative stability of different clusters with different criteria by employing Time DependentDensity Functional Theory and taking advantages of some computational packages like Octopus Quantum Espresso and FHI aims Then by exploiting OCTOPUS package optical absorption spectraof the clusters have been studied It has been found that optical properties of Tungsten Oxides clustersare size dependent In this package there are two different method for determining optical propertieswhich both have some flaw and flair Moreover Since the burden of calculation was heavy andfor coming sure about our results we started to investigate these properties with the new Liouville Lanczos method perturbative method which is recently written in Quantum Espresso All these threemethods showed a great consensus that is rewarding In addition optical gap of clusters have beenobtained and its behaviour has been reviewed as a function of size As it is mentioned before alterationof optical properties in presence of Hydrogen is well known therefore we started to incorporate ourclusters with H First it was essential to find the best position for Hydrogen thus different positionhave been verified by determining its adsorption energy As it is anticipated the best position forHydrogen in W O۳ n 1 n 5 is terminal Oxygen and for W O۳ ۶ is bridge Oxygen The corollarywas a red shift in optical spectra and all of optical gap have been largely decreased Before addingHydrogen the spectra did not have any peak in visible span that it means our clusters are transparentbut after incorporation of Hydrogen in these clusters there appeared some absorption peaks in visiblespan which means the transparency is gone and our materials are opaque now In general clusters color have changed to blue but still the color of them is size dependent and by varying size there isan infinitesimal change in their color In all of the clusters the ۶th one is completely different fromsmaller clusters and rather resemble the bulk by having some bulk like properties that make this clusterdue of importance Keywords Time Dependent Density functional theory Tungsten Oxides Optical properties Optical Spectra ofTransition Metal Oxides Time Propagation

داوري اصفهاني ، محمد مهدي

بررسي و مطالعه ابتدا به ساكن خواص اپتيكي نانو خوشه هاي اكسيد تنگستن و تاثير جذب هيدروژن به كمك رهيافت نظريه ي تابعي چگالي وابسته به زمان

طيف جذب اكسيد فلزات واسطه , انتشارگر زماني