Author Topic: some question about the MPSH  (Read 7671 times)

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Offline Roc

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some question about the MPSH
« on: January 6, 2009, 12:42 »
Dear everyone,

Like the picture as follows,When  caculating the "Projected Hamiltonian eigenstates" and “Projected Hamiltonian energy spectrum ”,we should choose the projected atoms, do you often just caculate the molecular or the total central scattering region(the molecular and the probe screening layers),  what are the differences between them?

Thanks!
« Last Edit: January 6, 2009, 14:15 by anyipeng »

Offline vihardabest

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Re: some question about the MPSH
« Reply #1 on: January 6, 2009, 13:31 »
Dear anyipeng,
I am not so sure what are the differences exactly because I didn't try it yet but I have this idea.
The only thing that I notice, for my systems, is that one or half of electron moves form the electrode to the channel. Thus, in this case, I would prefer to calculate "Projected Hamiltonian eigenstates" and “Projected Hamiltonian energy spectrum " for total center scattering region(the molecular and the probe screening layers) because the number of the electrons will be totally different compare with the number of electrons in isolated system.
I don't know if I help you but this is the first thing on the top of my head.
I am interest in this problem as well.



Offline ipsecog

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Re: some question about the MPSH
« Reply #2 on: January 6, 2009, 22:13 »
The main idea behind the MPSH concept is to calculate the spectrum for the molecule only (or even a segment of the molecule), in order to see the influence of the contacts on the molecular spectrum. The charge which is carried away into the leads in the open system naturally redistributes the charge configuration of the molecule, and this is an important reason for the modification of the spectrum. The level broadening doe to the coupling to the semi-infinite electrodes is another; to see this, you should however rather look at the surface density of states.

It can sometimes make sense to include the whole central region, but it will produce a huge amount of energy levels which are not really relevant, and it might become difficult to identify those that belong to the molecule. In this case, but also in general, one should always compute the density of states as well to ensure that the MPSH levels obtained are localized states (sharp peaks in the DOS).

Offline Roc

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Re: some question about the MPSH
« Reply #3 on: January 7, 2009, 02:28 »
Thank you ,ipsecog ! you are very kind! ;)

Offline Nordland

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Re: some question about the MPSH
« Reply #4 on: January 7, 2009, 14:37 »
When I am looking to the MPSH states, I only choose the molecule itself + the nearest neighbors of the molecule.

It should be noted that two flags 'include surfaces layers' and 'include molecule' only works if the twoprobe is build entirely within VNL, which I think it is a bit annoying.

Offline Roc

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Re: some question about the MPSH
« Reply #5 on: January 8, 2009, 04:34 »
 ;D,
Yeah! I have the fellow feeling with you, I expect the VNL tool improved more perfect!