Phonon transmission with bigger supercell for electrodes

[chem-william]

Hi, I'm trying to calculate the phonon transmission of different junctions with gold electrodes and a molecule in the middle. I'm a bit concerned about the resulting transmission as I've got substantial transmission at 0 omega (transmission > 1.0). I took a look at the settings that the dynamical matrix was calculated with and it said the following:

Code

repetitions                        = (1, 1, 3)

which makes sense given I've told it to only make 1, 1, 1 repetitions in the settings for the dynamical matrix. But, what I suspect is that this is not enough for the phonons to go to zero and that's why I get such high transmission at omega = 0. Is there any way to only make a bigger supercell for the electrodes, but not the unit cell? I'd like to avoid repeating the central region as it substantially increases the time to calculate the dynamical matrix.