How to do geometry optimization with defect?
Posted: Mon Nov 16, 2015 1:37 pm
I'm studying a material with 52 atoms in the unit cell. For the pure material I can do structural optimization and calculate other things just fine. However, when I substitute one of the atoms with an impurity atom, structural optimization is unable to converge. That is, the maximal force value (maxfor) goes like this:
Is it possible that it has something to do with changes in symmetry? I can see the following in my log file:
The pure material material has the tetragonal lattice. With a defect, I think it becomes monoclinic or triclinic. Should I modify the lattice constants and/or the primitive vectors slightly to help break the symmetry?
Code: Select all
2.539E-02
2.003E-02
1.416E-02
1.231E-02
1.480E-02
1.319E-02
1.930E-02
2.289E-02
2.301E-02
...Is it possible that it has something to do with changes in symmetry? I can see the following in my log file:
Code: Select all
--- !COMMENT
message: |
The Bravais lattice determined only from the primitive
vectors, bravais(1)= 4, is more symmetric
than the real one, iholohedry= 1, obtained by taking into
account the atomic positions. Start deforming the primitive vector set.
src_file: symbrav.F90
src_line: 201
...
symlatt : the Bravais lattice is mC (one-face-centered monoclinic)
--- !COMMENT
message: |
The Bravais lattice determined from modified primitive
vectors, bravais(1)= 2, has a lower symmetry than before,
but is still more symmetric than the real one, iholohedry= 1
obtained by taking into account the atomic positions.
src_file: symbrav.F90
src_line: 210
The pure material material has the tetragonal lattice. With a defect, I think it becomes monoclinic or triclinic. Should I modify the lattice constants and/or the primitive vectors slightly to help break the symmetry?