[Smeagol-discuss] Total Energy

[Simon Dubois]

Hello,
it's me again ;-)

I would like to bring some precisions to my previous post about the
calculation of the total energy. I am interested in the calculation of the
total energy for a system with open boundary conditions (e.g. molecule +
semi-infinite contacts).

As can be seen in the smeagol output, several parts of the total energy
are already computed. My questions are then:

- are these contributions to the total energy computed with the SCF
electronic density computed within smeagol (the one obtained from the
Gtreen's functions) ?

- in order to obtain the total energy of the system (the one with open
boundary conditions) do we simply need to add a term
E_self=Tr[(Self_L+Self_R)*rho] to the computed total energy?

Cheers,

Simon


> Dear Smeagol Users and Developpers,
>
> I have some questions related to the computation of the total energy in
Siesta and Smeagol.
>
> (a) I know that, due to the presence of the self-energies, the effective
SCF hamiltonian computed within smeagol is no more hermitian and that
the
> eigenenergies are thus complex number. However, if I am not mistaking,
the
> real part of these complex number still have the meaning of an energy
while the complex part is related to the quasi-particle lifetime. Is
that
> true ?
>
> (b) If the previous point is true, then, in order to compute the total
energy of the open boundary system, we should simply add a term
> E_self = trace([rho]*[self_L + self_R])
> to the total energy computed by Siesta.
>
> (c) I have noticed the following differences between the enregy terms
computed by Smeagol (left side) and Siesta (right side):
>
> siesta:-Eions   = -167171.565970       167171.565970
> siesta: Ena     =   14152.066946        14152.066948
> siesta: Ekin    =   82725.940493        82743.197427
> siesta: Enl     =  -29606.795074       -29621.564038
> siesta: DEna    =    1570.039623         1561.672622
> siesta: DUscf   =      73.434271           72.756367
> siesta: DUext   =       0.000000            0.000000
> siesta: Exc     =  -19114.634221       -19118.273918
> siesta: eta*DQ  =       0.000000            0.000000
> siesta: Emadel  =       0.000000            0.000000
> siesta: Ekinion =       0.000000            0.000000
> siesta: Eharris = -117371.513978      -117381.709241
> siesta: Etot    = -117371.513933      -117381.710563
> siesta: FreeEng = -117371.513933      -117381.742383
>
> Is it the NEGF density matrix which is used to compute these energies
within Smeagol ? In this case, do these differences simply originate in
the modification of the electronic density due to the presence of the
self-energies?
>
> Any comments are welcome..... Thanks in advance!
>
> Best wishes,
>
> Simon
>
> --
> Simon Dubois
>
> PhD Student
> Ecole Polytechnique de Louvain
> Unité de Physico-Chimie et de Physique des Matériaux (PCPM)
> Place Croix du Sud, 1
> B-1348 Louvain-La-Neuve (Belgium)
> Tel. 010/47.28.38
>
>
>
>
>
>
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>


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