1 / 19

Analyzing Energy Shift Effects on Orbital Range and Lattice Constant in Siesta Simulation of Bulk Al

The lecture discusses how to control the range of orbitals in a balanced way by implementing an energy shift in a confinement potential for the Particle in a Box model. It references the key work by C. Cohen-Tannoudji et al. on Quantum Mechanics. The Siesta simulation for bulk Al involves adjusting the PAO Energy Shift parameter to observe changes in orbital range, lattice constant, free energy, and computational efficiency per SCF step. The process is detailed, encompassing the manipulation of input files, running Siesta with varying energy shifts, and analyzing the results using gnuplot.

ziati
Download Presentation

Analyzing Energy Shift Effects on Orbital Range and Lattice Constant in Siesta Simulation of Bulk Al

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Exercises on basis set generation Control of the range: the energy shift Javier Junquera

  2. Most important reference followed in this lecture

  3. How to control the range of the orbitals in a balanced way: the energy shift Particle in a confinement potential: Imposing a finite + Continuous function and first derivative   E is quantized (not all values allowed) Increasing E  and tends to -  when x  has a node  +   Complement M III “ “Quantum Mechanics” ”, C. Cohen-Tannoudji et al.

  4. How to control de range of the orbitals in a balanced way: the energy shift Energy increase   Energy shift PAO.EnergyShift (energy) Cutoff radius, rc, = position where each orbital has the node A single parameter for all cutoff radii The larger the Energy shift, the shorter the rc’s Typical values: 100-200 meV E. Artacho et al. Phys. Stat. Solidi (b) 215, 809 (1999)

  5. Bulk Al, a metal that crystallizes in the fcc structure Go to the directory with the exercise on the energy-shift More information at the Siesta web page http://www.icmab.es/siesta and follow the link Documentations, Manual Inspect the input file, Al.energy-shift.fdf As starting point, we assume the theoretical lattice constant of bulk Al FCC lattice Sampling in k in the first Brillouin zone to achieve self-consistency

  6. For each basis set, a relaxation of the unit cell is performed Variables to control the Conjugate Gradient minimization Two constraints in the minimization: - the position of the atom in the unit cell (fixed at the origin) - the shear stresses are nullified to fix the angles between the unit cell lattice vectors to 60° °, typical of a fcc lattice

  7. The energy shift: Variables to control the range of the basis set

  8. The energy shift: Run SIESTA for different values of the PAO.EnergyShift Then, run SIESTA Edit the input file and set up PAO.EnergyShift 0.002 Ry $siesta < Al.energy-shift.fdf > Al.0.002.out

  9. For each energy shift, search for the range of the orbitals Edit each output file and search for:

  10. For each energy shift, search for the free energy Edit each output file and search for: We are interested in this number

  11. For each energy shift, search for the free energy Edit each output file and search for: We are interested in this number

  12. For each energy shift, search for the relaxed lattice constant Edit each output file and search for: The lattice constant in this particular case would be 2.108073 Å × × 2 = 4.216146 Å

  13. For each energy shift, search for the timer per SCF step We are interested in this number

  14. The energy shift: Run SIESTA for different values of the PAO.EnergyShift Then, run SIESTA Edit the input file and set up PAO.EnergyShift 0.002 Ry $siesta < Al.energy-shift.fdf > Al.0.002.out Try different values of the PAO.EnergyShift PAO.EnergyShift 0.005 Ry $siesta < Al.energy-shift.fdf > Al.0.005.out PAO.EnergyShift PAO.EnergyShift PAO.EnergyShift PAO.EnergyShift PAO.EnergyShift PAO.EnergyShift 0.010 Ry 0.015 Ry 0.020 Ry 0.025 Ry 0.030 Ry 0.035 Ry $siesta < Al.energy-shift.fdf > Al.0.010.out $siesta < Al.energy-shift.fdf > Al.0.015.out $siesta < Al.energy-shift.fdf > Al.0.020.out $siesta < Al.energy-shift.fdf > Al.0.025.out $siesta < Al.energy-shift.fdf > Al.0.030.out $siesta < Al.energy-shift.fdf > Al.0.035.out PAO.EnergyShift 0.040 Ry $siesta < Al.energy-shift.fdf > Al.0.040.out

  15. Analyzing the results Edit in a file (called, for instance, cutoff-ef.dat) the previous values as a function of the Energy shift

  16. Analyzing the results: range of the orbitals as a function of the energy shift $ gnuplot $ gnuplot> plot "cutoff-ef.dat" u 1:2 w l, "cutoff-ef.dat" u 1:3 w l $ gnuplot> set terminal postscript color $ gnuplot> set output “range.ps” $ gnuplot> replot

  17. Analyzing the results: lattice constant as a function of the energy shift $ gnuplot $ gnuplot> plot "cutoff-ef.dat" u 1:4 w l $ gnuplot> set terminal postscript color $ gnuplot> set output “latcon.ps” $ gnuplot> replot

  18. Analyzing the results: free energy as a function of the energy shift $ gnuplot $ gnuplot> plot "cutoff-ef.dat" u 1:5 w l $ gnuplot> set terminal postscript color $ gnuplot> set output “freener.ps” $ gnuplot> replot

  19. Analyzing the results: time per SCF step as a function of the energy shift $ gnuplot $ gnuplot> plot "cutoff-ef.dat" u 1:6 w l $ gnuplot> set terminal postscript color $ gnuplot> set output “timer.ps” $ gnuplot> replot

More Related