Dear Javad, it seems that mpi/mpi4py is not properly installed on your computer. You could test this by running: python3 -c "from mpi4py import MPI" on the command line, which will trow an import error, if this is indeed the case. Note that there is an additional step required on Windows, because mpi4py is not provided in the standard conda-forge channel, but it has to be installed separately: conda install -c intel mpi4py See the installation instructions https://kwant-project.org/extensions/tkwant/pre/installation for details. Hope this solves your problem. Best, Thomas ________________________________ From: tavakkolidjawad [tavakkolidjawad@ut.ac.ir] Sent: Monday, December 21, 2020 2:25 PM To: kwant-discuss@kwant-project.org Subject: [Kwant] MPI Error Hello to all Recently I installed tkwant using conda on Windows 10. When I try to run the program, I get the following error: from mpi4py import MPI ImportError: DLL load failed: The specified module could not be found. However, I downloaded the "mpi.py" file from Github again and put it in the tkwant folder, But this error still exists. How can I solve this problem? Thanks Javad Tavakkoli