Take-home postcard. Basis set: Atomic orbitals s p d f SIESTA: Strictly localized (zero beyond cut-off radius)

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Presentation transcript:

Take-home postcard

Basis set: Atomic orbitals s p d f SIESTA: Strictly localized (zero beyond cut-off radius)

Effective potential for valence electrons Pseudopotential r (a.u.) V(r) The internal electrons do not participate in the chemical bond

All electronPseudopotential Muffin-Tin LAPW Plane waves Localized Orbitals Simple taxonomy of Ab-initio codes

Pseudopotential generation Number of k-points Electronic temperature XC functional: LDA, GGAs Harris functional vs SCF Spin polarization SCF convergence tolerance Supercell size (solid & vacuum) Geometry relaxation tolerance Basis set: Size (SZ, DZ, DZP...) Range (Shape) Real space mesh cutoff Things to keep in mind Plane-wave cutoff SIESTAPW codes Lab Apparatus

Basis Size Quick and dirty calculations Highly converged calculations Complete multiple-ζ + Polarization + Diffuse orbitals Minimal basis set (single- ζ; SZ) Depending on the required accuracy and available computational power + Basis Optimization

Easy setup with reasonable defaults NumberOfSpecies 1 number-of-atoms 2 LatticeConstant 5.43 Ang %block LatticeVectors %endblock LatticeVectors %block ChemicalSpeciesLabel 1 14 Si %endblock ChemicalSpeciesLabel AtomicCoordinatesFormat Fractional %block AtomicCoordinatesAndAtomicSpecies Si Si 2 %endblock AtomicCoordinatesAndAtomicSpecies

Simple level of specification PAO.Basis.Size SZPSIZE PAO.EnergyShift 150 meVRANGE PAO.SplitNorm 0.25SHAPE # MeshCutoff 200 Ry

%block PAO.Basis H n= E n= %endblock PAO.Basis # Grid.Cell.Sampling T Higher degree of control

Real-Space Grid Eggbox effect

Emilio Artacho (Cambridge University) Pablo Ordejón (ICMAB, Barcelona) José M. Soler (UAM, Madrid) Julian Gale (Curtin Inst. of Tech., Perth) Richard Martin (U. Illinois, Urbana) Javier Junquera (U. Cantabria, Santander) Daniel Sánchez-Portal (UPV, San Sebastián) Eduardo Anglada (Nanotec) Alberto García (ICMAB, Barcelona) The SIESTA Team