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Nanodcal Nanodsim RESCU


Brief technical discussion about nanobase


Nanobase is an atomic code developed by NanoAcademic for solving relativistic all electron atoms, generating norm conserving non-local pseudopotential and the corresponding pseudo-atomic orbital, for use in other NanoAcademic software such as nanodcal. Nanobasis is written in Matlab.

 

 
An nanobase run contains the following five steps:
  1. In step-1, Dirac equation for all-electron single atom is solved self-consistently where electron-electron interaction is taken into account at LDA or various GGA level.
  2. Step-2, generating pseudopotential from the all-electron solution. In chemical processes, hopefully atomic cores do not play an important role. Therefore, atomc core and core orbitals can be effectively removed using pseudopotential. The method of Troullier-Martines pseudopotential is used. To properly calculate exchange-correlation potential of valence electrons, core correction is included. The pseudopotential is further transformed into the Kleinman-Bylander separable form that is used by nanodcal. Nanobase uses well established criterions to check and eliminate any ghost states in KB.
  3. Step-3 is an optional step to calculate logarithmic derivatives as function of energy for a given radius R. A comparison between all-electron and pseudopotential logarithmic derivative gives a check on the transferability of the pseudopotential. The comparison of pseudopotential (PS) and KB logarithmic derivative gives a check on the existence of ghost states. If something is wrong in the logarithmic derivatives, one can go back to the previous step and tune computation parameters. Steps 1-3 are general procedures of any pseudopotential generation.
  4. Step-4 is specific for the calculation scheme of nanodcal. In this step, orbitals that vanish at a finite cut off (i.e. confined) are generated from the pseudoptential.
  5. Finally, in step-5, nanobase exports basis data file. Typically, less than one minute is needed to complete these five steps using a laptop.
 



Nanobase is run using a single input file having five blocks of input data corresponding to the above five steps:

  • Parameters for calculating the all electron atom
  • Parameters for generating pseudopotential
  • Parameters for checking logarithmic derivative
  • Parameters for generating confined orbtial functions
  • Parameters for exporting data file.
     

More details can be found in the nanobase User Manual.