Calculation of optical properties and macroscopic polarization with SIESTA Daniel Sánchez-Portal Centro de Física de Materiales, Centro Mixto CSIC- UPV/EHU,San Sebastián, Spain Email: [email protected]Efficient density-functional calculations with atomic orbtitals: a hands-on tutorial on the SIESTA code CECAM Tutorial Lyon, June 18-22
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Calculation of optical properties and macroscopic polarization with SIESTA
Calculation of optical properties and macroscopic polarization with SIESTA. Daniel Sánchez-Portal Centro de Física de Materiales, Centro Mixto CSIC-UPV/EHU,San Sebastián , Spain Email: [email protected]. - PowerPoint PPT Presentation
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Calculation of optical properties and macroscopic polarization with SIESTA
Daniel Sánchez-Portal
Centro de Física de Materiales, Centro Mixto CSIC-UPV/EHU,San Sebastián, Spain
Polycrystal: Average over three spatial directions
What is left out in this approach
*Classical collective modes (plasmons). They can be included at the RPA level. Important at low energies for small systems, not that much for bulk.
*Excitonic effects (electron-hole interaccion). Quite hard to include
*Spectrum beyon Kohn-Sham approx. At the moment just the “scissor operator” to correct excitation energies.
Diamond and Silicon
Silicon
Diamond
SIESTAG.F. Bertsch et al.Phys.Rev. B 62, 7998 (2000).
PW, CASTEP DZP basis set (26 bands)
Optical response of 4-Å diameter SWCNT with SIESTA
Testing the accuaracy of SIESTA band structures on graphene:•Including a diffuse 3s orbital we have perfect with PW up to 6 eV•Adding an additional 3p shell the agreement is extended to 10-12 eV
Our band structures for the 4-Å are in very niceagreement with the PW calculations of Li et al.
In fact, ...
Optical response of 4-Å diameter SWCNT with SIESTA (cont.)