[CP2K-user] [CP2K:12807] Band alignment calculations

[Patrick Gono]

Dear Elham,

You need two calculations. A bulk calculation where you align the band
edges with respect to the average electrostatic potential. And a slab
calculation with vacuum, where you align the average electrostatic
potential in the center layers of the slab with respect to the vacuum
potential.

In CP2K, the average electrostatic potential over the whole cell is set to
zero. Hence, the bulk calculation only consists in running a CELL_OPT of a
big enough supercell, and taking the values of the Fermi level and the
HOMO-LUMO gap. The Fermi level represents the position of the valence band
with respect to the average electrostatic potential, and the Fermi level +
gap is then the conduction band. This calculation gives you the alignment
of the band edges with respect to the average electrostatic potential.

For the vacuum calculation, you have to make sure you have a thick enough
slab (so that the electrostatic potential in the middle layers behaves like
the bulk one) and a thick enough vacuum layer, so that there the potential
is flat. Run a GEO_OPT of the slab with vacuum, and then perform an ENERGY
calculation on the resulting geometry with the V_HARTREE_CUBE option in the
PRINT section inside DFT set to .TRUE.
Next, project the .cube file of the average potential along the axis
perpendicular to the interface. Then, take the value in the middle of the
vacuum region, and subtract the average over the central-most layer(s)
inside the slab. This gives you the alignment of the average electrostatic
potential with respect to vacuum.

You see now that combining the results of the two yields the desired
alignment.

Yours sincerely,
Patrick Gono

On Thu, 23 Jan 2020 at 14:27, Elham M.Goliaei <e.go... at gmail.com> wrote:

> Hi Patrick,
>     Thanks, it was informative, first, I wanna calculate band alignment
> versus vacuum, for example according to Fig. 1;
> https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.102.036402
>
> How can I do these calculation to get band alignment versus vacuum?
>
> All the best,
> Elham
>
>
>
>
>
> On Wed, Jan 22, 2020 at 6:33 AM Patrick Gono <patri... at gmail.com>
> wrote:
>
>> Dear Elham,
>>
>> In the work of Guo et al. referenced above, it is stated that a molecular
>> dynamics simulation at the level of PBE was performed at the desired
>> temperature. The projected density of states was averaged over the duration
>> of the simulation. Since the average PDOS has long tails at the band edges,
>> a linear extrapolation of the band edge PDOS was carried out. It is these
>> values that are used as the temperature corrected band edges. See Fig. 3 of
>> this paper by Wiktor et al.:
>> https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.1.022401
>>
>> It is possible that you require the use of a more advanced electronic
>> structure method, and hence ab initio molecular dynamics may not be
>> feasible. In that case, you can follow the approach outlined in the above
>> reference -- run MD at the semilocal level, select a set of configurations
>> from the trajectory, perform single point (ENERGY) calculations with your
>> desired method, compute the PDOS, average over all snapshots, and carry out
>> the linear extrapolation of the PDOS tails around the band gap mentioned
>> previously.
>>
>> Alternatively, a one shot calculation of the phonon spectrum can be used
>> to estimate the band gap renormalization due to finite temperature. See the
>> work by Prof. Giustino, for example:
>> https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.075125
>>
>> Hope this helps.
>> Yours sincerely,
>> Patrick Gono
>>
>> On Wed, 22 Jan 2020 at 14:39, Elham M.Goliaei <e.go... at gmail.com>
>> wrote:
>>
>>> Thanks, can you guide me how I  can calculate T-dependent corrections of
>>> the band edges (Eq. 4 and 5).
>>>
>>> All the best,
>>> Elham
>>>
>>>
>>>
>>> On Tue, Jan 21, 2020 at 4:27 AM Patrick Gono <patri... at gmail.com>
>>> wrote:
>>>
>>>> Dear Elham,
>>>>
>>>> I recommend the work by Guo et al. where the band alignment at the
>>>> semiconductor water interface is studied in detail:
>>>> https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.7b02619
>>>>
>>>> Yours sincerely,
>>>> Patrick Gono
>>>>
>>>> On Mon, 20 Jan 2020 at 11:07, Elham M.Goliaei <e.go... at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Matthias,
>>>>>
>>>>>    I wanna calculate band alignment of a semiconductor and band
>>>>> alignment at the semiconductor-water interface, can you guide me how to
>>>>> calculate.
>>>>>
>>>>> All the best,
>>>>> Elham
>>>>>
>>>>> --
>>>>> 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 cp... at googlegroups.com.
>>>>> To view this discussion on the web visit
>>>>> https://groups.google.com/d/msgid/cp2k/408361f6-4639-4338-b63f-ace47ceeabfe%40googlegroups.com
>>>>> <https://groups.google.com/d/msgid/cp2k/408361f6-4639-4338-b63f-ace47ceeabfe%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>> .
>>>>>
>>>> --
>>>> 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 cp... at googlegroups.com.
>>>> To view this discussion on the web visit
>>>> https://groups.google.com/d/msgid/cp2k/CAPL1_v-DETREjQUWmFAA26%2BLXxj%3DEdgf%2BCqibn4NOS44QHqpNw%40mail.gmail.com
>>>> <https://groups.google.com/d/msgid/cp2k/CAPL1_v-DETREjQUWmFAA26%2BLXxj%3DEdgf%2BCqibn4NOS44QHqpNw%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>> --
>>> 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 cp... at googlegroups.com.
>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/cp2k/CAK_aGnJSJF61f7caSHZ-5gR_sM-O28CymKxxxEwCJgVRy8%2BK0g%40mail.gmail.com
>>> <https://groups.google.com/d/msgid/cp2k/CAK_aGnJSJF61f7caSHZ-5gR_sM-O28CymKxxxEwCJgVRy8%2BK0g%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>> .
>>>
>> --
>> 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 cp... at googlegroups.com.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/cp2k/CAPL1_v_1NCmGQ9O-jF6JCxjeserx%3D0DEWquoyGM3SAr8Es9FHA%40mail.gmail.com
>> <https://groups.google.com/d/msgid/cp2k/CAPL1_v_1NCmGQ9O-jF6JCxjeserx%3D0DEWquoyGM3SAr8Es9FHA%40mail.gmail.com?utm_medium=email&utm_source=footer>
>> .
>>
> --
> 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 cp... at googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/cp2k/CAK_aGnKVr_mfZ%3DugyT9NmL%2BCiYONuo_qtsgsv5FgCqj-wvioNQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/cp2k/CAK_aGnKVr_mfZ%3DugyT9NmL%2BCiYONuo_qtsgsv5FgCqj-wvioNQ%40mail.gmail.com?utm_medium=email&utm_source=footer>
> .
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20200124/a6c599f1/attachment.htm>