# direction of voltage

What is the direction of voltage which we are giving in transiesta calculation?

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Siesta Edit question
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Last query:
2019-01-23
2019-01-28

## This question was reopened

 Nick Papior (nickpapior) said on 2019-01-23: #1

In Siesta 4.0 the voltage drop is along the 3rd lattice vector.

In Siesta 4.1 there is no *unified* direction as there may be any N electrodes. And thus it depends on your semi-infinite directions.

 maluneelambari (maluneelambari) said on 2019-01-23: #2

Thanks Nick Papior, that solved my question.

 maluneelambari (maluneelambari) said on 2019-01-23: #3

Is this voltage is per Angstrom ? Can I convert corresponding to 1V as electric field as 1ev/A^0 ?

 Nick Papior (nickpapior) said on 2019-01-23: #4

It is the difference between the two leads chemical potentials. The (local) electric field can be extracted from the potential profile.

 maluneelambari (maluneelambari) said on 2019-01-23: #5

I didn't get how to do this . Can you explain me how to extract this?

 Nick Papior (nickpapior) said on 2019-01-28: #6

You may see details regarding potential drop in the TS_02 tutorial for the TS-TBtrans-sisl tutorials:

https://github.com/zerothi/ts-tbt-sisl-tutorial

Once you have the potential profile you should easily be able to calculate the electric field using the standard formula.