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Tyberius
Tyberius
6:13 PM
4
A: How to perform carrier-doping in VASP

Chengcheng XiaoNELECT tag should do the trick. A number that's larger than the default value (which is automatically calculated by VASP to be the number of valence electrons in the system) gives you charge doping and a real number that's lower than the default value gives you hole doping. Note that one doesn't ...

Thanks a lot for this useful answer, the method is like this : - Do a normal calculation to know the default NELECT value. - Change that default value (adding/subtracting) to get (electron/hole) doping But how to know how much electrons you should add/substract ? — Chi Kou yesterday
You don't necessarily needs to do a normal calculation to know the default NELECT value. It can be calculated manually by checking the number of valence electrons for each element in the POTCAR file and multiply that number of electrons with the number of corresponding atoms in the POSCAR. As for how many electrons to add/substract. It depends on the carrier concentration you are aiming to achieve, you can calculate the carrier concentration using the method I mentioned in the answer. — Chengcheng Xiao yesterday
Sir, do I need to relax my structure again after changing NELECT ? or I just go for SCF, DOS... calculations ? Last question : If I want to achieve 0.5 carrier concentration, and I have NELECT = 272 as default, and supercell volume = 2466.03. What would be the value of NELECT ? — Chi Kou 13 hours ago
That depends, if the carrier concentration is small enough, I would try and relax the structure. Alternatively, if it's quite high, then I wouldn't bother relax the structure because it's a doping level that's probably not achievable using gate doping and other "non-intrusive" method. Can you tell me the unit you are using for your "0.5 carrier concentration" and "supercell volume"? — Chengcheng Xiao 10 hours ago
I am just trying to repeat this paper's work, So I can apply the method for other materials like CrI3: doi.org/10.1103/PhysRevB.103.075433 — Chi Kou 10 hours ago
Sir, what do they mean by 0.5 electron concentration per unit cell. — Chi Kou 9 hours ago
I haven't read that paper but I think they mean adding 0.5 electron to the total electron number (NELECT) of one unit cell. If that's the case, then you should set your NELECT to be 272.5 — Chengcheng Xiao 6 hours ago
 
 
3 hours later…
Chi Kou
Chi Kou
9:35 PM
In that paper, the authors say : " In our calculations, the doping concentrations of up to 0.75 hole per unit cell for hole doping or up to 0.75 electron per unit cell for electron doping are considered. The carrier density up to ≈10 ¹⁵ cm −2 has already been achieved in experiment by using an ionic liquid as a gate dielectric [56,57]. Here, the corresponding largest doping concentrations are 2.27×10¹⁴ , 2.02×10¹⁴ , and 1.70×10¹⁴ cm-²
for the monolayer MoCl 3 , MoBr 3 , and MoI 3 , respectively, indicating that they can be experimentally realized through currently advanced gating technologi…
 

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