Cell shape relaxation: k-points and symmetry
Moderators: Global Moderator, Moderator
-
- Newbie
- Posts: 13
- Joined: Wed Nov 20, 2013 5:01 pm
- License Nr.: 5-311
Cell shape relaxation: k-points and symmetry
Hello,
I am currently doing some structural optimization on ZnO, but my questions are may be more general. I apologize if similar questions have been already asked, but I haven't found them.
- Imagine I am performing a series of fixed volume relaxations (ISIF=4) in order to fit the E(V) curve with the Murnaghan equation of state. Since I allow for cell shape changes, the symmetry of the system may change. I found a lot of explications about the implications of this on the basis set, but what about k-points? Changes in the symmetry of the system may occur, so how is the k-point grid handled?
- Is it always a good idea to use EDIFFG<0 to perform relaxations? Imagine that you have a cubic system; because of symmetry reasons you don't have forces acting on the atoms for any value of the cell-paramter. So, how does the code find the equilibrium parameter in this case?
Thanks for your help.
I am currently doing some structural optimization on ZnO, but my questions are may be more general. I apologize if similar questions have been already asked, but I haven't found them.
- Imagine I am performing a series of fixed volume relaxations (ISIF=4) in order to fit the E(V) curve with the Murnaghan equation of state. Since I allow for cell shape changes, the symmetry of the system may change. I found a lot of explications about the implications of this on the basis set, but what about k-points? Changes in the symmetry of the system may occur, so how is the k-point grid handled?
- Is it always a good idea to use EDIFFG<0 to perform relaxations? Imagine that you have a cubic system; because of symmetry reasons you don't have forces acting on the atoms for any value of the cell-paramter. So, how does the code find the equilibrium parameter in this case?
Thanks for your help.
Last edited by sponza on Wed Nov 20, 2013 5:49 pm, edited 1 time in total.
-- -- --
LORENZO SPONZA
LORENZO SPONZA
-
- Global Moderator
- Posts: 1817
- Joined: Mon Nov 18, 2019 11:00 am
Re: Cell shape relaxation: k-points and symmetry
Hi,
We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.
Best wishes,
VASP