# nextnano.NEGF - Software for Quantum Transport

### nextnanomat

Software documentation

### nextnano++

Software documentation

Examples

### Parallelization

<Simulation_Parameter>
...
...
</Simulation_Parameter>

For optimal performances, we recommended that <Maximum_Number_of_Threads> does not exceed the number of physical cores (when hyperthreading is activated, the number of physical cores is half the one on logical processsors).

#### Parallelization in case of combined Temperature-Voltage sweep

In the case where a combined Temperature-Voltage sweep is used, there are two levels of parallelization. The first is at the level of the command <Threads> in the <SweepParameters> section.

<SweepParameters>
<SweepType>Temperature-Voltage</SweepType>
...
</SweepParameters>

The second level of parallelization occurs in the <Simulation_Parameter> section:

<Simulation_Parameter>
...
...
</Simulation_Parameter>

### Contributions of individual scattering processes

The following command allow to display self-energies and spectral functions for some specific mechanisms, like e.g. scattering due to optical phonons:

<Scattering>
...
<Separate_Scattering>yes</Separate_Scattering>
...
</Scattering>

This command is only for analysis purpose, and has no influence on the other calculated quantities. It only involves an additionnal calculation of self-energies and Green's functions. In each basis folder, a folder with the name of the scattering process will appear, containing the retarded self-energy and the spectral function arising only from the specific scattering mechanism. Hence this spectral function gives the contribution to broadening of an individual scattering process.

### Output format for 2D plots

By default, 2D plots are output in a VTK format (files with a .vtr extension). Gnuplot files are also generated (in a file explorer, double click on the file to generate the gnuplot figure).

In addition, to output 2D plots in a AVS/Express format (.fld extension), the following command “<FLD_format>” can be added in the <Output> section of the input file.

The following commands can be used to control the output formats:

<Output>
...
<VTK_format>yes</VTK_format>
<FLD_format>yes</FLD_format>
<Gnuplot_format>yes</Gnuplot_format>
...
</Output>

### Scaling 1D wavefunctions

In order to scale the output of the square of the wavefunctions (1D plots), the following command can be used:

<Output>
...
<ScaleWaveFunction>0.1</ScaleWaveFunction>
...
</Output>