Questions about the total energy of a twoprobe system!

[hhspace]

Hello, evergyone
    For ATK-Version 2008.10 (DFT edition), the manual shows that the total energy of a twoprobe system can be calculated and it mainly include three parts: Electron kinetic energy, Electrostatic energy, and Exchange-corr. energy. However, for ATK 10.8 (DFT edition) I find that for a twoprobe system or device configuration the total energy of it is divided into four parts: Electron kinetic energy, Exchange-corr. energy, Hartree energy, and Interaction energy with the pseudo potential ions and other electro-static external potentials.
    I want to know whether Electrostatic energy of ATK-Version 2008.10 equals to the sum of Hartree energy and Interaction energy of ATK 10.8? Is that true even when bias voltage is applied?

[hhspace]

Yes, you are correct. Do note however that ATK 10.8 doesn't actually compute the total energy for devices (although the function name would indicate so); it returns the free energy. There is a correction term which plays a role in particular at finite bias. The total energy is not a well-defined quantity unless there is charge conservation, which is not the case for open systems (device configurations).

Anders