On 05/07/18 11:52, Rajneesh Chaurasiya wrote:
In basic semiconductor, if the Fermi level is close to conduction band then its called n types semiconductor while if the Fermi level is close to the valance band is called p type semiconductor.
It the Fermi energy is *in* the conduction band, because of electrons doping, it is a m-type semiconductor. It the Fermi energy is in the valence band, because of hole doping, it is p-type.
If there is no doping, the Fermi energy is in the gap: the semiconductor is to all effects an insulator.
In most the software like Wien2k Fermi level is located close to the valance band means all states are filled upto that level and also remain same by applying the strain. but in espresso, its switch to valance band maxima and conduction band minima by according to applied strain. i think, its not acceptable. please correct if i am wrong.
I'm not sure I understand what's your complaint. The zero of the energy bands is somewhat arbitrary. If you have a precisely-defined Fermi energy, like in a metal where the position of Ef is strictly constrained by the number of electrons, than you can use it to align different calculations. If your Fermi energy is not so precisely defined, like in a insulator where you can put it anywhere in the gap, then you should use something else to align the bands: the maximum of the valence band is a possible choice.
Using a different type of smearing function (m-v, m-p, fd) could make the Fermi energy more stable. But the main point is that if you have a gap, it is usually better to treat your system as an insulator (occupations="fixed") and use the highest occupied level instead of the Fermi energy.
hth
On Thu, Jul 5, 2018 at 11:47 AM, Rajneesh Chaurasiya <[email protected] <mailto:[email protected]>> wrote:Dear All, I have computed the electronic band structure under the compression and tensile strain. Change in the conduction band minima and valance band maxima are slightly shifted with strain which i have also verified from the WIEN2K but when i add or subtract the Fermi energy, then i observed in some cases, Fermi level close to conduction and some cases the Fermi energy close to valance band. since by applying the strain the types of semiconductor behavior (n type or p type) does not change. then why the Fermi level is shifted close to valance band maxima or conduction band minima. such types of behavior are not observed in the WIEN2k. why the Fermi level is shifted according to strain?-- Thanks & RegardsRajneesh Chaurasiya Research Scholar IIT Jodhpur, India Mob. No. +91-9584499697 +91-7610950803 -- Thanks & Regards Rajneesh Chaurasiya Research Scholar IIT Jodhpur, India Mob. No. +91-9584499697 +91-7610950803 _______________________________________________ users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
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