# [CP2K:8672] How to calculate Fermi energy of metals?

ashish dabral ashishd... at gmail.com
Wed Feb 8 23:15:53 UTC 2017

```Hi Matt,

Yes, indeed I am looking for the chemical potential/ fermi energy (at 0K or
otherwise, assuming it doesn't change much with temperature).
I need to find the the highest occupied states with respect to the bottom
of conduction band for the metal. I would like to align semiconductors wrt
to the fermi energy to evaluate metal-semiconductor junction properties.

Thanks

On Wednesday, 8 February 2017 23:59:58 UTC+1, Matt W wrote:
>
> Hi,
>
> the OP might need to be a bit careful with the definition of the fermi
> energy and explain what they are after. I think there are different
> conventions around.
>
> I think the free-electron models he referred to, and that 7 eV for copper
> number, measure the chemical potential / fermi energy relative to the
> bottom of the band. So it corresponds to something like the energy from the
> lowest 4s copper states up to the highest occupied states. What you would
> use it for, I am not quite sure.
>
> So I think it is not the same thing as a physical measure relative to the
> vacuum, i.e. work function.
>
> Matt
>
> On Wednesday, February 8, 2017 at 10:15:19 PM UTC, Ari Paavo Seitsonen
> wrote:
>>
>> Dear Ashish Dabral,
>>
>>   The only way _I_ know is to calculate a system with surface (well, two,
>> slab model) and then align the Fermi energy via the potential in the middle
>> of the slab - should be thick enough so that in the middle it is converged
>> - and the potential in the middle of the vacuum. So the value of "Fermi
>> energy" would be the work function. I guess that one would get the same
>> value if one would then take the difference of the potential in the middle
>> of the slab and potential in the vacuum, and then uses that after aliging
>> the difference between the potential and the Fermi energy in a bulk system.
>>
>>   With GGA one usually gets too small values of the work function if I
>> remember correctly (self-interaction/asymptotics), by about 0.5-1 eV
>> depending on the material.
>>
>>     Greetings,
>>
>>        apsi
>>
>> 2017-02-08 17:17 GMT+01:00 ashish dabral <ashis... at gmail.com>:
>>
>>> Hi,
>>>
>>> I would like to know how to calculate the fermi energy of metals using
>>> cp2k.
>>> For example, Cu has a fermi energy of around 7.0eV, which can also be
>>> calculated using the general formula involving carrier concentration (
>>> https://en.wikipedia.org/wiki/Fermi_energy, the
>>> three dimensional case.) I would like to know how can I obtain this
>>> value (approximate) from the bulk metal unit cell.
>>>
>>> Thanks
>>>
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "cp2k" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to cp2k+... at googlegroups.com.
>>> To post to this group, send email to cp... at googlegroups.com.
>>> Visit this group at https://groups.google.com/group/cp2k.
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
>>
>>
>> --
>>
>> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
>>   Ari Paavo Seitsonen / Ari.P... at iki.fi / http://www.iki.fi/~apsi/
>>     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>>     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...