Error and Warning Messages

Quantum-Current-Poisson fails to converge

Most often Quantum-Current-Poisson calculation fails to converge because:

  1. The maximum number of iterations has been chosen too small.

    SOLUTION: Increase the number of iteration using iterations.

  2. The number of electron or hole eigenstates has been chosen too small.

    SOLUTION: Check the occupations in the files bias_*\Quantum\occupation_*.dat. If the occupation does not drop from the ground state to the highest excited state by several orders of magnitude, you need to calculate more states. If you are using one-band model or 6-band k⋅p model then you need to adjust a keyword attributes num_ev in Gamma{}, L{}, X{}, Delta{}, HH{}, LH{}, SO{} or in kp_6band{ }. In teh case of using 8-band k⋅p model, the number of states can be adjusted by num_electrons and num_holes in kp_8band{ }.

  3. The under-relaxation parameter has been chosen too large.

    SOLUTION: Check whether the solution oscillates, i.e., residuals do not drop continuously but increase in some iterations. Try to decrease the under-relaxation parameter controlled by alpha_fermi in order to damp the oscillations.

  4. The minimum charge density in the current equation has been chosen too small (currents{ } ==> minimum_density_*).

    SOLUTION: Try to increase the minimum charge densities to improve conditioning of the current equation. Relevant keywords are minimum_density_electrons and minimum_density_holes.

WARNING: Linear solver residual of ARPACK-INVERSE set too large in multiband quantum solver

Linear solver residual of ARPACK-INVERSE set too large in multiband quantum solver. ARPACK-INV solver uses internally the linear solver on each iteration, therefore the accuracy of ARPACK-INV is limited by accuracy of the linear solver. It is recommended to set the residuals of linear solver to be smaller than residuals of the ARPACK-INV, otherwise this warning is thrown. The residual of the ARPACK-INV can be set by a keyword accuracy. The linear solver residuals can be set by keywords linear_solver{ abs_accuracy } or linear_solver{ rel_accuracy }.

Error: (nodes number of coordinate 1) != (lines number in file)

Simulation *.log file contains the following error

error:(nodes number of coordinate 1) != (lines number in file)

It means that you have defined values at some grid points twice inside the imported file. Check if some points are duplicated in the file that you are trying to import. For example, you should avoid situation as the following:

…
1.0    0.5
1.1    0.5
1.2    0.5
1.2    0.6
1.3    0.6
…

In this case the point 1.2 is defined twice, which is the source of the problem.

nextnano++ exit code: -1073741795

Simulation *.log file contains the following exit code -1073741795 or other big negative number

(nextnano++ exit code: -1073741795)

Most likely you need to install the Microsoft Visual C++ Redistributable . Choose the corresponding version matching your operation system architecture (most likely X64) from the section Latest Microsoft Visual C++ Redistributable Version. It’s a typical error when running nextnano++ on Windows Server OS.

It is also possible that your CPU is not suited for nextnano++ executable, i.e., you are using processor from Pentium family, typical on old laptops. You can use nextnano++_Microsoft_32bit_serial.exe, see Error: The specified executable is not a valid application for this OS platform.

Other possibility is that your computer enters sleep mode during the runtime of your simulation. Turn off disable sleep mode on your computer to fix the problem.

nextnano++ exit code: -1

Simulation *.log file contains the following exit code -1

(nextnano++ exit code: -1)

It means that the simulation has been aborted by nextnanomat or by other means.

nextnano++ exit code: 1

Simulation *.log file contains the following exit code 1

(nextnano++ exit code: 1)

It means that there is error in the command line calling the solver.

nextnano++ exit code: 3

Simulation *.log file contains the following exit code 3

(nextnano++ exit code: 3)

There is a problem with validating your license.

Last update: 22/01/2025