User Tools
qcl:software_documentation
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
qcl:software_documentation [2017/03/16 09:22] thomas.grange |
qcl:software_documentation [2017/07/24 12:51] (current) thomas.grange |
||
|---|---|---|---|
| Line 1: | Line 1: | ||
| - | ===== nextnano.QCL - Software documentation ===== | + | ===== nextnano.QCL - General remarks ===== |
| - | + | ||
| - | ===== General remarks ===== | + | |
| nextnano.QCL is a console application that is run from within the [[http://www.nextnano.com/products/nextnanomat.php|nextnanomat]] software (GUI). Alternatively, it can be executed from the command line. The input file specifies the device that shall be simulated. | nextnano.QCL is a console application that is run from within the [[http://www.nextnano.com/products/nextnanomat.php|nextnanomat]] software (GUI). Alternatively, it can be executed from the command line. The input file specifies the device that shall be simulated. | ||
| Line 33: | Line 31: | ||
| If you have further questions, see the [[qcl:faq|FAQ]] or contact <support@nextnano.com>. | If you have further questions, see the [[qcl:faq|FAQ]] or contact <support@nextnano.com>. | ||
| - | ===== Working principle ===== | ||
| - | |||
| - | The code is based on the non-equilibrium Green's functions (NEGF) formalism (also known as the Keldysh, or Kadanoff-Baym formalism). This formalism allows to account for both quantum transport effects (i.e. coherent transport effects, such as resonant tunneling), as well as scattering mechanisms. | ||
| - | |||
| - | In the NEGF formalism, scattering processes are described in terms of self-energies. Self-energies and Green's functions are calculated in a self-consistent way, as both elastic and inelastic scattering processes are accounted within the the self-consistent Born approximation. | ||
| - | |||
| - | The code uses **field-periodic boundary condition**. | ||
| - | In this way the simulation accounts for an infinite periodic structure, with a periodic electric field. | ||
| - | Coherent transport between periods is accounted on a length set by ''<Coherence_length_in_Periods>''. | ||
| - | |||
| - | === Program flow === | ||
| - | |||
| - | {{ :qcl:flowchart.jpg?400 |}} | ||
| - | |||
| - | In the beginning of the calculation, the single-band effective mass Schrödinger equation is solved in real space. | ||
| - | The calculated energy levels and wave functions are then used as input to the NEGF algorithm. | ||
| - | The wave functions are termed **modes** and the NEGF algorithm is written in terms of **mode space** and not **real space** to make it computationally more efficient. | ||
| - | The number of QCL periods that are input to this Schrödinger equation are specified in ''<Number_of_lateral_periods_for_band_structure>''. | ||
| - | In general, the core of the NEGF algorithm should be rather independent of this number, e.g. | ||
| - | <code> | ||
| - | <Number_of_lateral_periods_for_band_structure> 4 | ||
| - | </Number_of_lateral_periods_for_band_structure> | ||
| - | </code> | ||
| - | should lead to very similar results compared to a value of ''5'' but the numerical values might differ slightly. | ||
| - | {{ :qcl:ldos_emin_emax_okay.jpg?200 |}} | ||
qcl/software_documentation.1489656134.txt.gz · Last modified: 2017/03/16 09:22 by thomas.grange
