Manganese in AFM fcc configuration

Message

giacomo giorgi · #1 Post by **giacomo giorgi** » Fri Jun 03, 2011 12:42 pm

Dear all,
in order to calculate the chemical potential of Manganese, I took into account the AFM configuration of the system in its fcc configuration.

The unit cell of this alpha-Mn is consituted by 58 atoms.

In my INCAR I set

SYSTEM = a-Mn
# xc
GGA = PE
VOSKOWN = 1
ISTART = 1
#electronic relaxation
LREAL = Auto
PREC= High
ENCUT= 500.0 eV
ENAUG= 605.4 eV
ISMEAR = 0
SIGMA = 0.05
#electronic RELAXATION
NELMIN = 4
NELM = 200
ISIF = 3
ISPIN=2
MAGMOM=29*1.5 29*-1.5
ICHARG=1
IBRION = 1
#accuracy of the calculation
EDIFF = 1.E-5
EDIFFG = -0.005 ! inizialmente -0.004
#ionic steps
NSW = 500
AMIX = 0.2
BMIX = 0.00001
AMIX_MAG = 0.8
BMIX_MAG = 0.00001
LORBIT = 11

In the OUTCAR I check the magnetization and I observe that

magnetization (x)

# of ion s p d tot
----------------------------------------
1 0.016 0.017 2.370 2.403
2 0.004 0.002 0.636 0.641
3 0.002 0.001 0.336 0.339
4 0.002 0.001 0.339 0.342
5 0.002 0.001 0.342 0.345
6 0.002 0.001 0.335 0.339
7 0.004 0.002 0.622 0.627
8 0.004 0.002 0.653 0.659
9 0.004 0.002 0.634 0.639
10 0.004 0.002 0.650 0.656
11 0.000 -0.002 -0.061 -0.063
12 0.000 -0.002 -0.063 -0.065
13 -0.001 -0.002 -0.072 -0.075
14 -0.001 -0.002 -0.069 -0.071
15 -0.001 -0.002 -0.081 -0.084
16 -0.001 -0.002 -0.086 -0.088
17 -0.001 -0.002 -0.103 -0.106
18 -0.001 -0.002 -0.104 -0.107
19 -0.001 -0.002 -0.105 -0.108
20 -0.001 -0.002 -0.094 -0.097
21 -0.001 -0.002 -0.107 -0.110
22 -0.001 -0.002 -0.090 -0.093
23 -0.001 -0.003 -0.136 -0.140
24 -0.001 -0.003 -0.138 -0.142
25 -0.002 -0.003 -0.147 -0.151
26 -0.002 -0.003 -0.144 -0.148
27 -0.002 -0.003 -0.162 -0.167
28 -0.002 -0.003 -0.165 -0.169
29 -0.002 -0.003 -0.184 -0.189
30 -0.002 -0.003 -0.187 -0.192
31 -0.002 -0.003 -0.186 -0.191
32 -0.002 -0.003 -0.171 -0.176
33 -0.002 -0.003 -0.189 -0.194
34 -0.002 -0.003 -0.170 -0.175
35 -0.003 -0.006 0.018 0.009
36 -0.003 -0.006 0.015 0.006
37 -0.003 -0.006 0.012 0.003
38 -0.003 -0.006 0.013 0.004
39 -0.003 -0.006 0.022 0.013
40 -0.003 -0.006 0.020 0.012
41 -0.003 -0.006 0.023 0.014
42 -0.003 -0.006 0.021 0.013
43 -0.003 -0.006 0.023 0.014
44 -0.003 -0.006 0.016 0.007
45 -0.003 -0.006 0.020 0.012
46 -0.003 -0.006 0.017 0.008
47 -0.002 -0.003 0.000 -0.004
48 -0.002 -0.003 -0.001 -0.005
49 -0.002 -0.003 -0.005 -0.010
50 -0.002 -0.003 -0.003 -0.008
51 -0.001 -0.003 0.004 -0.001
52 -0.002 -0.003 0.002 -0.003
53 -0.001 -0.003 0.003 -0.001
54 -0.001 -0.003 0.003 -0.002
55 -0.001 -0.003 0.002 -0.002
56 -0.002 -0.003 -0.003 -0.007
57 -0.001 -0.003 0.002 -0.003
58 -0.002 -0.003 -0.001 -0.005
------------------------------------------------
tot -0.036 -0.137 4.124 3.952

Even if I am very new with magnetic systems I understand by myself that there is something of "wrong".....
Could you kindly help me in understanding?

My very best,
Giacomo

forsdan · #2 Post by **forsdan** » Fri Jun 03, 2011 5:13 pm

Can you supply your POSCAR file as well?

giacomo giorgi · #3 Post by **giacomo giorgi** » Sat Jun 04, 2011 6:31 am

Hi Forsdan,
I found these coordinates in a couple of crystallographic site. I also attach you the POTCAR header. Thanks!
G

Mn
1.00000000000000
8.921 0.00 0.00
0.000 8.921 0.00
0.00 0.00 8.921
58
Selective dynamics
Direct
0.00000 0.00000 0.00000 T T T
0.50000 0.50000 0.50000 T T T
0.31700 0.31700 0.31700 T TT
0.31700 0.68300 0.68300 T T T
0.68300 0.68300 0.31700 T T T
0.68300 0.31700 0.68300 T T T
0.81700 0.81700 0.81700 T T T
0.81700 0.18300 0.18300 T T T
0.18300 0.18300 0.81700 T T T
0.18300 0.81700 0.18300 T T T
0.35600 0.35600 0.04200 T T T
0.35600 0.64400 0.95800 T T T
0.64400 0.64400 0.04200 T T T
0.64400 0.35600 0.95800 T T T
0.64400 0.04200 0.64400 TT T
0.64400 0.95800 0.35600 T T T
0.95800 0.64400 0.35600 T T T
0.04200 0.64400 0.64400 T T T
0.04200 0.35600 0.35600 T T T
0.35600 0.04200 0.35600 TT T
0.95800 0.35600 0.64400 T TT
0.35600 0.95800 0.64400 T T T
0.85600 0.85600 0.54200 T T T
0.85600 0.14400 0.45800 T T T
0.14400 0.14400 0.54200 T T T
0.14400 0.85600 0.45800 T T T
0.14400 0.54200 0.14400 T T T
0.14400 0.45800 0.85600 T T T
0.45800 0.14400 0.85600 T T T
0.54200 0.14400 0.14400 T T T
0.54200 0.85600 0.85600 T T T
0.85600 0.54200 0.85600 T T T
0.45800 0.85600 0.14400 T T T
0.85600 0.45800 0.14400 T T T
0.08900 0.08900 0.27800 T T T
0.08900 0.91100 0.72200 T T T
0.91100 0.91100 0.27800 T T T
0.91100 0.08900 0.72200 T T T
0.91100 0.27800 0.91100 T T T
0.91100 0.72200 0.08900 T TT
0.72200 0.91100 0.08900 T T T
0.27800 0.91100 0.91100 T T T
0.27800 0.08900 0.08900 T T T
0.08900 0.27800 0.08900 T T T
0.72200 0.08900 0.91100 T T T
0.08900 0.72200 0.91100 T T T
0.58900 0.58900 0.77800 T T T
0.58900 0.41100 0.22200 T T T
0.41100 0.41100 0.77800 T T T
0.41100 0.58900 0.22200 T T T
0.41100 0.77800 0.41100 T T T
0.41100 0.22200 0.58900 T T T
0.22200 0.41100 0.58900 T T T
0.77800 0.41100 0.41100 T T T
0.77800 0.58900 0.58900 T T T
0.58900 0.77800 0.58900 T T T
0.22200 0.58900 0.41100 T T T
0.58900 0.22200 0.41100 T T T

PAW_PBE Mn_pv 07Sep2000
13.0000000000000000
parameters from PSCTR are:
VRHFIN =Mn: 3p4s3d
LEXCH = PE
EATOM = 2024.8347 eV, 148.8212 Ry

forsdan · #4 Post by **forsdan** » Sat Jun 04, 2011 11:39 am

First of all I don't know if you would classify the alpha-Mn structure (A12-structure) as a class of the fcc-structure, since it is very far from the textbook fcc structure. Anyhow, if alpha-Mn is the structure you want to use then I suggest you to plot the structure together with your assigned initial magnetic moments. Because then you will see than it makes no sense. You have broken symmetries in your magnetic moments and while the cell itself is AFM there is no layered AFM to speak of. The latter is not required but it seems you were after such a structure.

I suggest you to doublecheck what you actually want to calculate. Because based on the structure and the assigned MAGMOM tag, your results seem that they could be reasonable.

Cheers,
/Dan