`lead.cell_hamiltonian()` gives 32000. The thickness of my slab is
50. Is this something not possible to calculate?
I have (stupidly) tried to copy two slices in central region (one for each lead). After 3 hours, the memory blows up. My workstation has 128Gb DDR4 memory. (kwant is compiled against mumps 5.0.1 and multithreading is working)