applying Strain to find changes in bandstructure

[wizard S]

Can anybody tell me how do i apply strain in a material Quantum espresso input file .once i find scf ,nscf I can plot bandstructure and finds changes in bandstructure. 

[KK M]

Hi Wizard

Do you know the concept of applying strain? 

I asking because i did it in VASP, but not in QE. but concept is exactly same. So if you know how to do in VASP same way just change the input lattice coordinates. And do rest

On Sat, 14 Dec 2024, 3:13 am wizard S, <ashou...@gmail.com> wrote:

Can anybody tell me how do i apply strain in a material Quantum espresso input file .once i find scf ,nscf I can plot bandstructure and finds changes in bandstructure. 

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[KK M]

it should work. i suppose. this is similar to VASP almost. try this and let me know here. if it works.

this is equivalent to 2% strain elongation (tensile strain)

On Sun, Dec 15, 2024 at 4:40 AM wizard S <ashou...@gmail.com> wrote:

I use vesta. QE,burai,boltztrap.
Never used vasp.
Chatgpt suggested cell parameter section in pic. Is it correct way?

[KK M]

if you ever know the input file of VASP that is POSCAR, we only change one lattice parameter at a time and do rest of calculations.

suppose lattice a direction you want 2% strain (enlarge) make it to multiply by 1.02. then do single paint calculation with band structure related inputs. then draw band for that percentage

On Sun, Dec 15, 2024 at 4:53 AM wizard S <ashou...@gmail.com> wrote:

But how would i know that its strained?
Does this also changes atomic position cordinates?

[KK M]

EDIT to above response: the response above given assuming unidirectional lattice change is your target,

[Thamizh Arasan]

If you haven't got idea mail me

To view this discussion visit https://groups.google.com/d/msgid/quantumespresso/CADsoCrVVvytyJ6o84KgkXBACcMux7XXGNZm4dE6xWnwB2NiHCg%40mail.gmail.com.

[KK M]

please discuss in the chat here, so that it is useful for all. 

[KK M]

hmm.

strain means the crystal is under 'strain' without changing the 'physical atomic positions' within the crystal. but the crystal lattice dimensions are changed, so the 'coordinates with respect to earlier crystal lattice will change if u again relax the cell (computationally). but because you want the effect of strain on band structure, what we do is only change the lattice parameter in the desire direction and without relaxing the cell (mind you the earlier coordinates number will not be edited) we do band structure calculation, then the resultant band is the effect of such strain. again i am saying what the method we do in VASP, so the concept should be same here as well. May be QE experts also comment here, please for everyone's benefit on the subject. that is the intention of this group, please.

On Sun, Dec 15, 2024 at 5:12 AM wizard S <ashou...@gmail.com> wrote:

But its not changing atomic cordinates.
Theoritycally and practically when stran is applied on an material both lattice contant and atomic position changes as interatomic distance is larger!

[Thamizh Arasan]

Sure! But seems like vasp being a new religion. There are people just plug and play, unlike qe.
First you should fix the volume (or) axis as V_0
Then V_x = V_0 times (x) percentage of variation
Then do scf
Then nscf
Then band structure plot 
Remeber that  kpoints and symmetry are must be same.

[KK M]

Thanks a lot Thamizh. for suggesting as per QE. appreciate the discussions here. !!!

[Thamizh Arasan]

Glad to help you! KK

[KK M]

please follow as Thamizh mentioned as per QE. it could give the results as desired.

On Sun, Dec 15, 2024 at 5:37 AM wizard S <ashou...@gmail.com> wrote:

If atomic position stays fixed only lattice constant changes,

Doesnt that produce wrong results as real world strain also changes atomic position? 

[wizard S]

If atomic position stays fixed only lattice constant changes,

Doesnt that produce wrong results as real world strain also changes atomic position? 

[wizard S]

But its not changing atomic cordinates.
Theoritycally and practically when stran is applied on an material both lattice contant and atomic position changes as interatomic distance is larger!

[wizard S]

I use vesta. QE,burai,boltztrap.
Never used vasp.
Chatgpt suggested cell parameter section in pic. Is it correct way?

On Sat, Dec 14, 2024, 8:53 AM KK M <kkmwo...@gmail.com> wrote:

[wizard S]

But how would i know that its strained?
Does this also changes atomic position cordinates?