total moment on the cell and Hund's rule
Posted: Thu Jul 07, 2005 8:06 pm
Dear Vaspusers
I did a calculation of single Pt atom in a large cell (box size 15 A,
1-kt, PAW91, GGA91) with LORBMOM and LORBIT. LSORBIT tag
turn on in the INCAR file.
However, the values of orbital moments and spin moments
I get are not consistent with empirical Hund's rule.
The Pt PP file has valence configuration 5d96s1 ie PP's are
already generated in the atomic ground state configuration and
not in bulk configuration. So I should get
spin moment on Pt atom = 2 bohr magnetons as there are two
unparied electrons each spin 1/2 and electron g factor is 2.
orbital moment = 2 bohr magneton as L=2 for d-orbital.
since the LNONCOLLINEAR tag is automatically on, I get
three components of orbital moments and three components
of spin moments printed in the OUTCAR file.
when I square each component, add it up and then take the
square root I get
spin-moment on Pt sphere : 0.989 bohr magneton
orbital moment on Pt sphere: 1.05 bohr magneton
spin-moment on the cell : 1.61 bohr magneton
I expected the spin-moment on the cell to be exactly 2 as per
Hund's rule if
we take into account the arbitrariness in first two values associated with the sphere size.
The sign seems to be correct for more than half filled atomic
shell in this case both L and S points in the same direction when I look into the sign of each orbital and spin components.
But the spin-moment magnitude is wrong.
My INCAR file:
ISPIN=2
PREC=high
NELMIN=5
NELM=70
EDIFF=1E-05
LSORBIT=.TRUE.
LORBIT= 11
LORBMOM=.TRUE.
ISMEAR =0
SIGMA =0.001
LREAL=F
GGA=91
VOSKOWN=1
Since PP is already generated in the ground state, Do I have
to still follow the suggested receipe for the free atom
ie either NUPDOWN = number of unpaired electrons in the atom
or use FERWE and FERDO and occupy the states according to
the Hund's rule,
ISMEAR=-2 to keep the occupancies fixed
SIGMA= very small say 0.00001
LDIAG= .FALSE. to keep the ordering of the eigenstates fixed.
to do the free atom calculation and to get the correct spin-moment on the cell.
How to get the correct orbital moment on the cell.
sahu
I did a calculation of single Pt atom in a large cell (box size 15 A,
1-kt, PAW91, GGA91) with LORBMOM and LORBIT. LSORBIT tag
turn on in the INCAR file.
However, the values of orbital moments and spin moments
I get are not consistent with empirical Hund's rule.
The Pt PP file has valence configuration 5d96s1 ie PP's are
already generated in the atomic ground state configuration and
not in bulk configuration. So I should get
spin moment on Pt atom = 2 bohr magnetons as there are two
unparied electrons each spin 1/2 and electron g factor is 2.
orbital moment = 2 bohr magneton as L=2 for d-orbital.
since the LNONCOLLINEAR tag is automatically on, I get
three components of orbital moments and three components
of spin moments printed in the OUTCAR file.
when I square each component, add it up and then take the
square root I get
spin-moment on Pt sphere : 0.989 bohr magneton
orbital moment on Pt sphere: 1.05 bohr magneton
spin-moment on the cell : 1.61 bohr magneton
I expected the spin-moment on the cell to be exactly 2 as per
Hund's rule if
we take into account the arbitrariness in first two values associated with the sphere size.
The sign seems to be correct for more than half filled atomic
shell in this case both L and S points in the same direction when I look into the sign of each orbital and spin components.
But the spin-moment magnitude is wrong.
My INCAR file:
ISPIN=2
PREC=high
NELMIN=5
NELM=70
EDIFF=1E-05
LSORBIT=.TRUE.
LORBIT= 11
LORBMOM=.TRUE.
ISMEAR =0
SIGMA =0.001
LREAL=F
GGA=91
VOSKOWN=1
Since PP is already generated in the ground state, Do I have
to still follow the suggested receipe for the free atom
ie either NUPDOWN = number of unpaired electrons in the atom
or use FERWE and FERDO and occupy the states according to
the Hund's rule,
ISMEAR=-2 to keep the occupancies fixed
SIGMA= very small say 0.00001
LDIAG= .FALSE. to keep the ordering of the eigenstates fixed.
to do the free atom calculation and to get the correct spin-moment on the cell.
How to get the correct orbital moment on the cell.
sahu