Energy of free atom
Posted: Tue May 23, 2017 11:36 pm
There are several posts discussing this issue.
1)
What I am curious is about the energy level filling of d vs s orbitals. I tried several transition metal elements Ti, V, Pd etc. What I see is that first d orbitals are filled instead of s orbitals. See below for Pd atom. This configuration is d5 s1 (spin 1) and d4 (spin 2) = d9 s1. But, shouldn't the s orbitals be filled before d giving s1 d5 and d4 = s1d9?
PROCAR new format
# of k-points: 1 # of bands: 10 # of ions: 1
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -7.28949549 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.895 0.895
band 2 # energy -7.12080615 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 3 # energy -6.84744581 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.890 0.890
band 4 # energy -6.75985025 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.890 0.890
band 5 # energy -6.71846832 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.889 0.889
band 6 # energy -4.66346711 # occ. 1.00000000
ion s p d tot
1 0.283 0.000 0.000 0.283
......zero occ. for others
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -6.20103008 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 2 # energy -6.17344224 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 3 # energy -6.16403739 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 4 # energy -5.89965505 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.892 0.892
...zero occ. for others
#INCAR for above:
ENCUT = 450.000000
BMIX = 0.000100
AMIX = 0.200000
SIGMA = 0.002000
EDIFF = 1.00e-05
PREC = Normal
ALGO = 38
ISYM = 0
ISPIN = 2
ISMEAR = 0
ISTART = 0
ICHARG = 1 #multiple runs were done
NELM = 100
NSW = 0
NPAR = 1
IVDW = 12
LCHARG = .TRUE.
LWAVE = .TRUE.
MAGMOM = 2
LORBIT=10
#POSCAR
12x13x14 Angstroms with atom at 0,0,0
#KPOINTS
Monkhorst pack, gamma point
#POTCAR
PAW_PBE
2) For Cr, setting nupdown=6 gives the correct orbital ordering where s is filled first followed by d giving s1d5 configuration.
3) I also tried the two step process of converging the atomic energies using icharg=11 and ismear=-2 (and other tags) as given in the manual. Again for several metals like Ti, V, etc, I see that d orbitals are filled first instead of s. Irrespective of the reference potentials (bulk or free atom) used to generate potcar, shouldn't the energy ordering be such that s is filled first and then d is filled?
For example, below is a case for Ti (with 10 electrons in POTCAR). In the first step, where icharg=11, s orbitals are filled first followed by d orbitals as they should be. However, when I set ISMEAR=-2 in the second step, the order reverses after the SCF step and d orbitals are filled first.
band 1 # energy -36.48590817 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 2 # energy -36.48589961 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 3 # energy -36.48587414 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 4 # energy -3.82214452 # occ. 1.00000000
ion s p d tot
1 0.206 0.000 0.000 0.206
band 5 # energy -2.44033563 # occ. 0.49670291
ion s p d tot
1 0.000 0.000 0.791 0.791
band 6 # energy -2.44005237 # occ. 0.41739660
ion s p d tot
1 0.000 0.000 0.791 0.791
band 7 # energy -2.43990042 # occ. 0.37600046
ion s p d tot
1 0.000 0.000 0.791 0.791
band 8 # energy -2.43985117 # occ. 0.36285946
ion s p d tot
1 0.000 0.000 0.791 0.791
band 9 # energy -2.43979107 # occ. 0.34704057
ion s p d tot
1 0.000 0.000 0.791 0.791
band 10 # energy -1.12719640 # occ. 0.00000000
ion s p d tot
1 0.000 0.064 0.000 0.064
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -34.58759976 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 2 # energy -34.58759079 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 3 # energy -34.58756878 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 4 # energy -3.37716078 # occ. 1.00000000
ion s p d tot
1 0.187 0.000 0.000 0.187
...rest zero occ.
4) Is there a way to make the calculation converge to sn dm configuration instead of dm sn (m,n are just number of electrons in d and s orbitals)? We can identify using icharg=11 calculation as to which orbital is filled first (as shown in (3)) but doing a following SCF step leads to dm sn instead of sn dm configuration.
5) How reliable are the energies I obtain for sn dm configuration vs dm sn?
6) On a different note, when reading PROCAR files, sometimes occupation within the same band for two orbitals (say s and d) are very close (say 0.1 and 0.2). I know that PROCAR makes an spherical shell approximation but how (if at all I should) do I interpret very close occupations between two orbitals?
1)
What I am curious is about the energy level filling of d vs s orbitals. I tried several transition metal elements Ti, V, Pd etc. What I see is that first d orbitals are filled instead of s orbitals. See below for Pd atom. This configuration is d5 s1 (spin 1) and d4 (spin 2) = d9 s1. But, shouldn't the s orbitals be filled before d giving s1 d5 and d4 = s1d9?
PROCAR new format
# of k-points: 1 # of bands: 10 # of ions: 1
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -7.28949549 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.895 0.895
band 2 # energy -7.12080615 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 3 # energy -6.84744581 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.890 0.890
band 4 # energy -6.75985025 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.890 0.890
band 5 # energy -6.71846832 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.889 0.889
band 6 # energy -4.66346711 # occ. 1.00000000
ion s p d tot
1 0.283 0.000 0.000 0.283
......zero occ. for others
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -6.20103008 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 2 # energy -6.17344224 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 3 # energy -6.16403739 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.894 0.894
band 4 # energy -5.89965505 # occ. 1.00000000
ion s p d tot
1 0.000 0.000 0.892 0.892
...zero occ. for others
#INCAR for above:
ENCUT = 450.000000
BMIX = 0.000100
AMIX = 0.200000
SIGMA = 0.002000
EDIFF = 1.00e-05
PREC = Normal
ALGO = 38
ISYM = 0
ISPIN = 2
ISMEAR = 0
ISTART = 0
ICHARG = 1 #multiple runs were done
NELM = 100
NSW = 0
NPAR = 1
IVDW = 12
LCHARG = .TRUE.
LWAVE = .TRUE.
MAGMOM = 2
LORBIT=10
#POSCAR
12x13x14 Angstroms with atom at 0,0,0
#KPOINTS
Monkhorst pack, gamma point
#POTCAR
PAW_PBE
2) For Cr, setting nupdown=6 gives the correct orbital ordering where s is filled first followed by d giving s1d5 configuration.
3) I also tried the two step process of converging the atomic energies using icharg=11 and ismear=-2 (and other tags) as given in the manual. Again for several metals like Ti, V, etc, I see that d orbitals are filled first instead of s. Irrespective of the reference potentials (bulk or free atom) used to generate potcar, shouldn't the energy ordering be such that s is filled first and then d is filled?
For example, below is a case for Ti (with 10 electrons in POTCAR). In the first step, where icharg=11, s orbitals are filled first followed by d orbitals as they should be. However, when I set ISMEAR=-2 in the second step, the order reverses after the SCF step and d orbitals are filled first.
band 1 # energy -36.48590817 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 2 # energy -36.48589961 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 3 # energy -36.48587414 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 4 # energy -3.82214452 # occ. 1.00000000
ion s p d tot
1 0.206 0.000 0.000 0.206
band 5 # energy -2.44033563 # occ. 0.49670291
ion s p d tot
1 0.000 0.000 0.791 0.791
band 6 # energy -2.44005237 # occ. 0.41739660
ion s p d tot
1 0.000 0.000 0.791 0.791
band 7 # energy -2.43990042 # occ. 0.37600046
ion s p d tot
1 0.000 0.000 0.791 0.791
band 8 # energy -2.43985117 # occ. 0.36285946
ion s p d tot
1 0.000 0.000 0.791 0.791
band 9 # energy -2.43979107 # occ. 0.34704057
ion s p d tot
1 0.000 0.000 0.791 0.791
band 10 # energy -1.12719640 # occ. 0.00000000
ion s p d tot
1 0.000 0.064 0.000 0.064
k-point 1 : 0.00000000 0.00000000 0.00000000 weight = 1.00000000
band 1 # energy -34.58759976 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 2 # energy -34.58759079 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 3 # energy -34.58756878 # occ. 1.00000000
ion s p d tot
1 0.000 0.991 0.000 0.991
band 4 # energy -3.37716078 # occ. 1.00000000
ion s p d tot
1 0.187 0.000 0.000 0.187
...rest zero occ.
4) Is there a way to make the calculation converge to sn dm configuration instead of dm sn (m,n are just number of electrons in d and s orbitals)? We can identify using icharg=11 calculation as to which orbital is filled first (as shown in (3)) but doing a following SCF step leads to dm sn instead of sn dm configuration.
5) How reliable are the energies I obtain for sn dm configuration vs dm sn?
6) On a different note, when reading PROCAR files, sometimes occupation within the same band for two orbitals (say s and d) are very close (say 0.1 and 0.2). I know that PROCAR makes an spherical shell approximation but how (if at all I should) do I interpret very close occupations between two orbitals?