Capacitance of a silicon line

Dear all,

I'm to calculate the (static or dynamic) capacitance of a silicon wire shown in the Figure below. When a bias is applied to the metal electrodes, a current passes through the silicon wire. And by using Suprem, I can calculate the 3-D charge density inside the silicon wire, say rho(r) where r is the 3-D position vector.



Now, I want to calculate the capacitance of the wire as a function of rho(r). Could you please give an idea?

Regards,