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Charge convergence for non-equilibrium transport
Date: 2020/08/12 02:33
Name: Samuel Dechamps   <>

Dear all,

I'd like to run non-equilibrium Green's function (NEGF) calculations for some specific systems.

I did beforehand some preliminary tests for the carbon chain in order to get a proper understanding of the convergence in the non-equilibrium case.

I'm focusing my analysis on the Mulliken charges (MC) at the edges of the extended central region.
Indeed, a recurrent issue in NEGF calculations is to obtained a flat electrostatic potential at the edges which would correspond to MC being identical to the ones in the lead.

However, I'm always obtaining MC that are 5% to 10% off.
For example (VDS=.5eV) :
1 C 2.030866540 2.030866540 4.061733080 0.000000000
2 C 2.011709486 2.011709486 4.023418972 0.000000000
3 C 2.121442689 2.121442689 4.242885378 0.000000000
4 C 1.915513226 1.915513226 3.831026451 0.000000000

I've played with many parameters without success.
For example :
-increase the mixing history, the Pulay start
-decrease the mixing weight
-set the Band iteration to 0
-switch the Poisson solver to finite differences
-extend the central region and the leads

However, the MC are not changing (meaning the excess MC would be intrinsic to VDS ?).

How can I reduce the excess charges ?

Thanks for your consideration,
S. Dechamps

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