Use of Quantum Mechanical Calculations to Investigate Small Silicon Carbide Clusters

<p>Silicon carbide (SiC) has a wide band gap at high temperature a good candidate material to meet future Air Force needs for wide-band-gap semiconductor devices for optoelectronics and high power electronics in aerospace applications. Defects generated during growth and fabrication are largely responsible for degradation of SiC properties so surface chemistry of SiC is very important in the surface fabrication and control of epitaxial SiC films. Computer simulation is an economic and efficient approach to model the surface chemistry of silicon carbide. A hybrid quantum mechanics/molecular mechanics (QM/MM) method had been proven a sufficient way to model bulk SiC surfaces. In this method a small cluster modeled by a QM method is embedded in a bulk framework that can be modeled by a MM method. The key to use the QM/MM to model silicon carbide surface chemistry is to find a QM method that can accurately model the silicon carbide clusters. Density Functional Theory (DFT) is chosen as a QM calculation method in this paper. Comparing the DFT calculation results with experimental results the calculation results of geometry predictions electron affinities (EA) and vibration frequencies are in good agreement with the experimental results. Sixteen optimized ground state structures were found using DFT:3BLYP method for the SimCn ... system. A root mean square average EA offset of -0.1 eV is found compared with the available experimental results. The factors that affect the accuracy of electron affinity calculation are discussed. The CPU time scaling of DFT calculations in SiC systems is also discussed.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p>