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SUMMARY:Modeling charged defects and defect levels in semiconductors and o
 xides with density functional theory – an improved\, inside-out perspect
 ive
DTSTART:20161017T143000
DTEND:20161017T153000
DTSTAMP:20260508T174117Z
UID:d8aa1e23491ff0008fcc4fb7645afd2dbbd6e56715e30d1bb4ac9bce
CATEGORIES:Conferences - Seminars
DESCRIPTION:Peter A. Schultz\, Sandia National Laboratories\, Albuquerque\
 , New Mexico\, USA.\nBio : Dr. Peter A. Schultz is a Principal Member of T
 echnical Staff at Sandia National Laboratories in the Multiscale Science D
 epartment.  Since 2008\, he has served as an Executive Editor for Modelin
 g and Simulation in Material Science and Engineering (MSMSE)\, appointed a
 s co-Editor-in-Chief in 2016. His research since he arrived at Sandia in 1
 992 has focused on the development of multiscale materials modeling method
 s requiring high-performance computing.  He is the principal developer of
  the SeqQuest code (http://dft.sandia.gov/Quest/)\, a parallel local-basis
  DFT pseudopotential code\, used as a computational platform to enable lar
 ge-scale simulations of defect physics and materials chemistry\, particula
 rly emphasizing applications in radiation effects in electronics.\nAbstrac
 t : The fundamental band gap defines a semiconductor\, and defects in semi
 conductors—when intentional\, called dopants\, when not\, impurities and
  lattice imperfections—introduce electron and hole traps within the gap 
 that modify the performance of an electronic device.  Density functional 
 theory (DFT) has emerged as an important tool to probe microscopic process
 es in materials and particularly defects in semiconductors.  However\, th
 e conventional DFT band gap is often half or less of the experimental band
  gap\, widely known as the DFT “band gap problem”.  As the band gap d
 efines the relevant energy scale for defect levels\, this appears to precl
 ude DFT for quantitative studies for charged defects that underlie much of
  the defect chemistry governing interesting semiconductor behavior.  Impl
 ementing a method incorporating rigorous boundary conditions for net charg
 e in supercells\, I find that a ‘defect band gap’\, the computed range
  of energies accessible to localized defect charge transitions\, is mostly
  insensitive to the size of the crystal Kohn-Sham gap.  Moreover\, the co
 mputed defect band gap agrees well with experimental band gap for many sem
 iconductors and insulators.  This provides insight into the DFT ‘band g
 ap problem’\, but also defines and validates best practices for modeling
  and simulation.  With validated accuracy in defect level predictions acr
 oss the full experimental band gap\, this demonstrates conventional DFT ca
 n be used for quantitative basic research into ionic and covalent material
 s. --- Sandia National Laboratories is a multi-program laboratory managed 
 and operated by Sandia Corporation\, a wholly owned subsidiary of Lockheed
  Martin Corporation\, for the U.S. Department of Energy’s National Nucle
 ar Security Administration under contract DE-AC04-94AL85000
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STATUS:CONFIRMED
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