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Table of Contents
Introduction
A Python/C based package, available at http://github.com/ProkopHapala/ProbeParticleModel/tree/PPSTM, which primary purpose is to simulate STM or dI/dV signal obtained with tilting tip apex (like CO, or Xe tip). It is based on the original PPAFM Python/C by Prokop Hapala and Co. http://github.com/ProkopHapala/ProbeParticleModel/ for simulation of tilting tip apex' AFM images.
You can get it easily from terminal by running these two commands:
git clone http://github.com/ProkopHapala/ProbeParticleModel/ cd ProbeParticleModel git checkout PPSTM
Basic Principles
The PP-STM code calculates an STM or dI/dV signal based on the input from various Linear Combination of Atomic Orbitals (LCAO)-DFT codes. These inputs are eigen-energies of eigen-states (molecular orbitals) and LCAO coefficients (for each state and atomic orbital of sample). Sample can be approximated by freestanding molecule, or by full system - molecule/substrate.
Software requirements
Necessary:
python-2.7; python-2.7-numpy(-1.8); gcc(-4.8); python-2.7-matplotlib(-1.3) - for plotting of figures;
Optional:
python-ase(-3.8.1) - needed for reading of FHI-AIMS inputs and GPAW input; GPAW - needed for reading of GPAW input;
Inputs for DFT Codes
Running PP-STM
PP-AFM pre-calculations
PP-STM calculations
- input parameters
- reading input files
- running fixed tip STM calculations
- running PP-dI/dV
Example
Theoretical prediction for Coronene molecule modified with with four nitrogen atoms :
LDA predicted HOMO for this molecule:
and LUMO:
Example test outputs
Example of scans over this molecule, with different probing orbitals and different scanning modes (AFM, STM, dI/dV … ).
Scans at the energy of HOMO:
Scans at the energy of LUMO:
