Re: [Wien] Is it possible artificially shift Fermi level for optical calculations?

2014-11-11 Thread Peter Blaha

I'm not sure I understand. How should EF affect your calculation of optics ?

Is this a metal or an insulator ?

If you want a bigger gap you can use a scissors-shift in case.inkram.


On 11/10/2014 06:28 PM, Martin Gmitra wrote:

Dear Wien2k users,

I am dealing with a slab system having a significant dipole moment.
Therefore, there is a Fermi level offset. I would like to calculate
optical properties of the system while I need to artificially shift
Fermi level. Do you have an idea how to do that?

Best regards,
Martin Gmitra, Uni Regensburg
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Re: [Wien] Is it possible artificially shift Fermi level for optical calculations?

2014-11-11 Thread Martin Gmitra
My system is a metal, and should be a semimetal (it is graphene on a
semiconduncting surface). Wien2k gives hole doping of graphene. Once a
dipole correction would be included (cross-checked in Quantum
Espresso), the Fermi level should lie at the Dirac point. From there
came my question about shifting of the Fermi level. The Fermi level in
fact determines which transitions from occupied to unoccupied states
take place.

Best regards,
Martin Gmitra

On Tue, Nov 11, 2014 at 9:48 AM, Peter Blaha
pbl...@theochem.tuwien.ac.at wrote:
 I'm not sure I understand. How should EF affect your calculation of optics ?

 Is this a metal or an insulator ?

 If you want a bigger gap you can use a scissors-shift in case.inkram.



 On 11/10/2014 06:28 PM, Martin Gmitra wrote:

 Dear Wien2k users,

 I am dealing with a slab system having a significant dipole moment.
 Therefore, there is a Fermi level offset. I would like to calculate
 optical properties of the system while I need to artificially shift
 Fermi level. Do you have an idea how to do that?

 Best regards,
 Martin Gmitra, Uni Regensburg
 ___
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 SEARCH the MAILING-LIST at:
 http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html


 --

   P.Blaha
 --
 Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
 Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
 Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
 WWW:   http://www.imc.tuwien.ac.at/staff/tc_group_e.php
 --
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Re: [Wien] Is it possible artificially shift Fermi level for optical calculations?

2014-11-11 Thread Peter Blaha

a) Is it necessary that you create a supercell with such a dipole ?
   Can't you put the graphene on both sides and make a symmetric slab ?

b) The easiest way is probably to rerun   x lapw2 -fermi with different 
NE in case.in2. Vary NE until EF is where you want it. However, I don't 
think it helps you much with optic. When you change EF in this way, your 
semiconductor is a metal and you will include such transitions in the 
optic calculations.


If suggestion a) is not possible ?? one could eventually add an electric 
field, but all these things are uncontrolled approximations. If graphene 
is affected by the semiconductor, you need a simulation cell which is 
large enough to do it right.


On 11/11/2014 02:46 PM, Martin Gmitra wrote:

My system is a metal, and should be a semimetal (it is graphene on a
semiconduncting surface). Wien2k gives hole doping of graphene. Once a
dipole correction would be included (cross-checked in Quantum
Espresso), the Fermi level should lie at the Dirac point. From there
came my question about shifting of the Fermi level. The Fermi level in
fact determines which transitions from occupied to unoccupied states
take place.

Best regards,
Martin Gmitra

On Tue, Nov 11, 2014 at 9:48 AM, Peter Blaha
pbl...@theochem.tuwien.ac.at wrote:

I'm not sure I understand. How should EF affect your calculation of optics ?

Is this a metal or an insulator ?

If you want a bigger gap you can use a scissors-shift in case.inkram.



On 11/10/2014 06:28 PM, Martin Gmitra wrote:


Dear Wien2k users,

I am dealing with a slab system having a significant dipole moment.
Therefore, there is a Fermi level offset. I would like to calculate
optical properties of the system while I need to artificially shift
Fermi level. Do you have an idea how to do that?

Best regards,
Martin Gmitra, Uni Regensburg
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--

   P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
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--

  P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
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[Wien] Is it possible artificially shift Fermi level for optical calculations?

2014-11-10 Thread Martin Gmitra
Dear Wien2k users,

I am dealing with a slab system having a significant dipole moment.
Therefore, there is a Fermi level offset. I would like to calculate
optical properties of the system while I need to artificially shift
Fermi level. Do you have an idea how to do that?

Best regards,
Martin Gmitra, Uni Regensburg
___
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