[Wien] why artificial lowering of symmetry changes the total energy?
katrusiat
katrusiat at yandex.ru
Wed Apr 16 15:24:14 CEST 2008
Dear Stefaan,
To be exact, I have never calculated the high-symmetry case, but only the cases with a symmetry reduced in different ways, that is, picking up Cu pairs in a different way.
For example, the high-symmetry (62_Pnma) unit cell can be reduced into:
{1} - (26 Pmc21)
or
{2} - (11 P21/m).
The total FM energy of {1} is -152655.214439 Ry
and that of {2} is -152655.214842 Ry
The precision of both calculations was 0.000001 Ry since all the figures after the point are important for me.
I am including the case.dmatdn files of both cases. There are differences between the density matrices of {1} and {2}, but I do not know what they mean physically.
{1}.dmatdn:
5 atom density matrix
2 0.000000 0.000000 0.000000 L, Lx,Ly,Lz in global orthogonal system
0.88397491E+00 0.45772788E-17 -0.30112862E-16 0.33756139E-17
-0.56905374E-01 -0.15502970E+00 -0.43813795E-16 -0.73875955E-17
0.52324299E-01 -0.44662464E-01
-0.30185041E-16 -0.14924055E-16 0.95408779E+00 0.18112910E-21
0.47708400E-16 -0.13402175E-15 0.28855650E-03 0.50914101E-03
0.43087170E-16 0.15093138E-16
-0.56905374E-01 0.15502970E+00 0.45714984E-16 0.17002143E-15
0.52349246E+00 -0.27031453E-32 -0.48102197E-16 0.16346734E-15
-0.56905374E-01 -0.15502970E+00
-0.41193459E-16 0.59607913E-17 0.28855650E-03 -0.50914101E-03
-0.47367892E-16 -0.13707573E-15 0.95408779E+00 -0.18112910E-21
0.26808369E-16 -0.10963618E-16
0.52324299E-01 0.44662464E-01 0.43516606E-16 0.90640477E-18
-0.56905374E-01 0.15502970E+00 0.29642355E-16 0.51200139E-17
0.88397491E+00 -0.65160781E-17
12 atom density matrix
2 0.000000 0.000000 0.000000 L, Lx,Ly,Lz in global orthogonal system
0.88397855E+00 0.59494382E-17 -0.29332059E-16 0.15369247E-17
-0.56903686E-01 -0.15502442E+00 -0.43751283E-16 -0.44684061E-17
0.52322421E-01 -0.44661108E-01
-0.29778323E-16 -0.21703198E-16 0.95408899E+00 0.18112910E-21
0.48457200E-16 -0.14148853E-15 0.28854483E-03 0.50909782E-03
0.45130372E-16 0.44197062E-17
-0.56903686E-01 0.15502442E+00 0.45677459E-16 0.17463781E-15
0.52350765E+00 -0.18439027E-32 -0.48146709E-16 0.17406951E-15
-0.56903686E-01 -0.15502442E+00
-0.41648997E-16 0.98869904E-17 0.28854483E-03 -0.50909782E-03
-0.51275854E-16 -0.14339813E-15 0.95408899E+00 -0.18112910E-21
0.29503689E-16 -0.20466146E-16
0.52322421E-01 0.44661108E-01 0.44185682E-16 0.13095126E-17
-0.56903686E-01 0.15502442E+00 0.30179069E-16 -0.14347071E-16
0.88397855E+00 -0.56814652E-17
and
{2}.dmatdn:
5 atom density matrix
2 0.000000 0.000000 0.000000 L, Lx,Ly,Lz in global orthogonal system
0.88622892E+00 0.00000000E+00 -0.14182705E-12 -0.19969227E-12
-0.56403834E-01 0.15378237E+00 0.63378789E-12 -0.24981983E-12
0.50668787E-01 0.43222111E-01
-0.14182705E-12 0.19969227E-12 0.95421135E+00 0.00000000E+00
-0.33383734E-12 -0.44952174E-12 0.27467590E-03 -0.48623493E-03
-0.63378789E-12 0.24981983E-12
-0.56403834E-01 -0.15378237E+00 -0.33383734E-12 0.44952174E-12
0.51579922E+00 0.00000000E+00 0.33383734E-12 0.44952174E-12
-0.56403834E-01 0.15378237E+00
0.63378789E-12 0.24981983E-12 0.27467590E-03 0.48623493E-03
0.33383734E-12 -0.44952174E-12 0.95421135E+00 0.00000000E+00
0.14182705E-12 0.19969227E-12
0.50668787E-01 -0.43222111E-01 -0.63378789E-12 -0.24981983E-12
-0.56403834E-01 -0.15378237E+00 0.14182705E-12 -0.19969227E-12
0.88622892E+00 0.00000000E+00
12 atom density matrix
2 0.000000 0.000000 0.000000 L, Lx,Ly,Lz in global orthogonal system
0.88622701E+00 0.00000000E+00 0.54373017E-13 -0.18285763E-13
-0.56343328E-01 -0.15380725E+00 -0.14830471E-12 0.10198634E-12
0.50701253E-01 -0.43187447E-01
0.54373017E-13 0.18285763E-13 0.95421141E+00 0.00000000E+00
-0.97651269E-14 -0.18678439E-12 0.27045235E-03 0.48783445E-03
0.14830471E-12 -0.10198634E-12
-0.56343328E-01 0.15380725E+00 -0.97651269E-14 0.18678439E-12
0.51580042E+00 0.00000000E+00 0.97651269E-14 0.18678439E-12
-0.56343328E-01 -0.15380725E+00
-0.14830471E-12 -0.10198634E-12 0.27045235E-03 -0.48783445E-03
0.97651269E-14 -0.18678439E-12 0.95421141E+00 0.00000000E+00
-0.54373017E-13 0.18285763E-13
0.50701253E-01 0.43187447E-01 0.14830471E-12 0.10198634E-12
-0.56343328E-01 0.15380725E+00 -0.54373017E-13 -0.18285763E-13
0.88622701E+00 0.00000000E+00
Thanks for help,
Kateryna
_______________________________________________________
1) How large is your energy change? Perhaps it is just numerical noise?
2) If the change is large enough, and if it is a lowering of the
energy upon symmetry reduction, you might have an onset of orbital
ordering. Inspect the density matrices of the two inequivalent
Cu-sites (dmat files), and see whether they are different from each
other and/or different from the density matrix for the high-symmetry
case. If there are differences, then this material apparently can
lower its total energy by occupying the Cu-d orbitals in different
ways in the two Cu-sites.
Stefaan
Quoting katrusiat <katrusiat at yandex.ru>:
> Dear all,
>
> I perform ferromagnetic (FM) (I make it FM by modifying the
> case.inst file accordingly) GGA+U calculations of the total energy
> of Cs2CuCl4, the compound with 4 equivalent magnetic Cu's in a unit
> cell. When I create an artificial unit cell of a lower symmetry with
> 2 inequivalent pairs of Cu's: Cu1 and Cu2, and again perform a FM
> GGA+U calculation, the total energy of the system is slightly
> different.
>
> By lowering the symmetry I only add labels to Cu's making them
> inequivalent, and also the crystallographic axes are interchanged in
> the new unit cell. So, why after these seemingly harmless actions
> the total energy should change?
>
> Thank you,
> Kateryna Foyevtsova
--
Яндекс.Почта. Чище не бывает http://mail.yandex.ru/nospam Я
_______________________________________________________
1) How large is your energy change? Perhaps it is just numerical noise?
2) If the change is large enough, and if it is a lowering of the
energy upon symmetry reduction, you might have an onset of orbital
ordering. Inspect the density matrices of the two inequivalent
Cu-sites (dmat files), and see whether they are different from each
other and/or different from the density matrix for the high-symmetry
case. If there are differences, then this material apparently can
lower its total energy by occupying the Cu-d orbitals in different
ways in the two Cu-sites.
Stefaan
Quoting katrusiat <katrusiat at yandex.ru>:
> Dear all,
>
> I perform ferromagnetic (FM) (I make it FM by modifying the
> case.inst file accordingly) GGA+U calculations of the total energy
> of Cs2CuCl4, the compound with 4 equivalent magnetic Cu's in a unit
> cell. When I create an artificial unit cell of a lower symmetry with
> 2 inequivalent pairs of Cu's: Cu1 and Cu2, and again perform a FM
> GGA+U calculation, the total energy of the system is slightly
> different.
>
> By lowering the symmetry I only add labels to Cu's making them
> inequivalent, and also the crystallographic axes are interchanged in
> the new unit cell. So, why after these seemingly harmless actions
> the total energy should change?
>
> Thank you,
> Kateryna Foyevtsova
--
Яндекс.Почта. Чище не бывает http://mail.yandex.ru/nospam Я
_______________________________________________________
1) How large is your energy change? Perhaps it is just numerical noise?
2) If the change is large enough, and if it is a lowering of the
energy upon symmetry reduction, you might have an onset of orbital
ordering. Inspect the density matrices of the two inequivalent
Cu-sites (dmat files), and see whether they are different from each
other and/or different from the density matrix for the high-symmetry
case. If there are differences, then this material apparently can
lower its total energy by occupying the Cu-d orbitals in different
ways in the two Cu-sites.
Stefaan
Quoting katrusiat <katrusiat at yandex.ru>:
> Dear all,
>
> I perform ferromagnetic (FM) (I make it FM by modifying the
> case.inst file accordingly) GGA+U calculations of the total energy
> of Cs2CuCl4, the compound with 4 equivalent magnetic Cu's in a unit
> cell. When I create an artificial unit cell of a lower symmetry with
> 2 inequivalent pairs of Cu's: Cu1 and Cu2, and again perform a FM
> GGA+U calculation, the total energy of the system is slightly
> different.
>
> By lowering the symmetry I only add labels to Cu's making them
> inequivalent, and also the crystallographic axes are interchanged in
> the new unit cell. So, why after these seemingly harmless actions
> the total energy should change?
>
> Thank you,
> Kateryna Foyevtsova
More information about the Wien
mailing list