Virtual Synthesis and Optoelectronic Properties of Prismatic Artificial Molecules of In-N and Zn-O: Comparative Studies
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0959-M05-02
Virtual Synthesis and Optoelectronic Properties of Prismatic Artificial Molecules of In-N and Zn-O: Comparative Studies Liudmila A. Pozhar1, Gail J. Brown2, and William C. Mitchel2 1 The Center for Materials for Information Technology, University of Alabama, P.O. Box 870209, Tuscaloosa, AL, 35487-0209 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, 3005 Hobson Way, Bldg. 651, Wright-Patterson AFB, OH, 45433-7707
ABSTRACT The Hartree-Fock (HF), restricted open shell HF (ROHF), configuration interaction (CI), complete active space (ICASCF), and multiconfiguration self-consistent field (MCSCF) methods provide sophisticated fundamental theory-based, computational tools to study structure, composition,chemistry and electronic properties of small artificial molecules composed of semiconductor compound atoms. These tools are used to synthesize virtually several prismatic In-N and Zn-O artificial molecules whose structure is derived from that of the symmetry elements of the respective wurtzite bulk lattices. Applications of spatial constraints to the atomic coordinates allow modeling molecular synthesis in quantum confinement, to obtain pre-designed molecules with tunable electronic properties. Relaxation of these constraints, or optimization, leads to the corresponding molecules synthesized in “vacuum”. Comparison of the obtained results for the pre-designed and vacuum molecules proves that small changes in atomic positions cause a significant change in the electronic properties. The obtained results confirm and ascertain previously reported tendencies and correlate with available experimental data. In particular, the large OTE of the pre-designed Zn6O6 molecule confirms to the experimental data reported recently for somewhat larger stoichiometric ZnO clusters. The OTE of the pre-designed In6N6 molecule coincides with experimental data for somewhat larger clusters.
INTRODUCTION Current “bottom-up” methods of experimental synthesis of arrays of small quantum dots (QDs) composed of semiconductor compound atoms realize nanoheterostructures (NHSs) based on units that are from about a hundred to thousands of atoms in size. Further increase in the density of elements of NHSs requires scaling down the size of the NHS units, thus minimizing the QD size to include only a few atoms (artificial molecules) whose electronic properties should be finely tuned to specific applications. While this task is beyond means of the contemporary experimental technologies, virtual (i.e., fundamental theory-based, computational) synthesis method can be used to provide theoretical predictions for physico-chemical properties of the artificial molecules, including those nucleated and stabilized in quantum confinement, on surfaces and at interfaces, to guide experimental developments in the near future. One of such major approaches to virtual synthesis, HF/ROHF/CI/CASSCF/MCSCF methods, realized by the GAMESS software package and successfully applied to virtual synthesis of
zincblende-derived pre-designed and va
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