Calculating transmission spectrum of dithiol benzene (DTB) device with gate elec

[mephisto3142001]

I constructed a dithiol benzene (DTB) device instructed from the tutorial "Calculate and analyze a molecular device configuration". After that, I added dielectric region(4ε0) and metallic region(-1 volt) as gate electrode using Builder and then I calculated TransmissionSpectrum (gate voltage was set to be 0 volt). The result was quite weird and very different from the original DTB device without gate electrode. I want to know what the problem it is and find a proper way to solve it. I posted python code and result figure.

[Anders Blom]

Having a metallic region with 0 V is not the same thing as not having a metallic region. The metallic region has a fixed electrostatic potential, so you are changing the boundary conditions. And if you use periodic b.c. (as is default) and yet have a fixed voltage at this point in space, there is an inconsistency which can lead to incorrect results.