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Title: Theoretical investigation of stabilities and optical properties of Si{sub 12}C{sub 12} clusters

By sorting through hundreds of globally stable Si{sub 12}C{sub 12} isomers using a potential surface search and using simulated annealing, we have identified low-energy structures. Unlike isomers knit together by Si–C bonds, the lowest energy isomers have segregated carbon and silicon regions that maximize stronger C–C bonding. Positing that charge separation between the carbon and silicon regions would produce interesting optical absorption in these cluster molecules, we used time-dependent density functional theory to compare the calculated optical properties of four isomers representing structural classes having different types of silicon and carbon segregation regions. Absorptions involving charge transfer between segregated carbon and silicon regions produce lower excitation energies than do structures having alternating Si–C bonding for which frontier orbital charge transfer is exclusively from separated carbon atoms to silicon atoms. The most stable Si{sub 12}C{sub 12} isomer at temperatures below 1100 K is unique as regards its high symmetry and large optical oscillator strength in the visible blue. Its high-energy and low-energy visible transitions (1.15 eV and 2.56 eV) are nearly pure one-electron silicon-to-carbon transitions, while an intermediate energy transition (1.28 eV) is a nearly pure carbon-to-silicon one-electron charge transfer.
Authors:
 [1] ;  [2] ;  [3]
  1. Air Force Research Laboratory DoD Supercomputer Resource Center, Wright-Patterson Air Force Base, Ohio 45433 (United States)
  2. (United States)
  3. Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433 (United States)
Publication Date:
OSTI Identifier:
22416011
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 3; Other Information: (c) 2015 U.S. Government; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ANNEALING; ATOMS; CARBON; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; DENSITY FUNCTIONAL METHOD; ELECTRONS; EV RANGE; EXCITATION; ISOMERS; MOLECULAR CLUSTERS; MOLECULES; OPTICAL PROPERTIES; OSCILLATOR STRENGTHS; POTENTIALS; SEGREGATION; SILICON; TIME DEPENDENCE