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Difference between revisions of "Alpha-AlF3"

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(Used INCAR Tags)
(Download)
 
(9 intermediate revisions by the same user not shown)
Line 23: Line 23:
  
  
*INCAR
+
*{{FILE|INCAR}}
<pre>
 
  SYSTEM      =  Al F3
 
  
   GGA          = PE
+
   {{TAGBL|SYSTEM}}      =  Al F3
   ISTART      = 1
+
  {{TAGBL|GGA}}         = PE
   ICHARG      = 0
+
   {{TAGBL|ISTART}}       = 1
   INIWAV      = 1
+
   {{TAGBL|ICHARG}}       = 0
   LREAL        =  AUTO
+
   {{TAGBL|INIWAV}}       = 1
   ISYM        = 2
+
   {{TAGBL|LREAL}}       =  AUTO
   ISPIN        = 1
+
   {{TAGBL|ISYM}}         = 2
 +
   {{TAGBL|ISPIN}}       = 1
  
 
Ionic minimisation
 
Ionic minimisation
   NSW          = 0
+
   {{TAGBL|NSW}}         = 0
   ISIF        = 2
+
   {{TAGBL|ISIF}}         = 2
   IBRION      = 2
+
   {{TAGBL|IBRION}}       = 2
#  EDIFFG      = -2E-2
+
{{TAGBL|EDIFFG}}       = -2E-2
   POTIM        = 0.1
+
   {{TAGBL|POTIM}}       = 0.1
  
 
Electronic minimisation
 
Electronic minimisation
   IALGO        = 38
+
   {{TAGBL|IALGO}}       = 38
 
+
   {{TAGBL|LWAVE}}       = .TRUE.
   LWAVE        = .TRUE.
+
   {{TAGBL|EMIN}}         =  -20.0
 
+
   {{TAGBL|EMAX}}         =  10.0
   EMIN        =  -20.0
+
   {{TAGBL|NEDOS}}       = 1601
   EMAX        =  10.0
 
   NEDOS        = 1601
 
  
 
EFG Calculation
 
EFG Calculation
   LEFG        = .TRUE.
+
   {{TAGBL|LEFG}}         = .TRUE.
   QUAD_EFG    = 146.6 0.0
+
   {{TAGBL|QUAD_EFG}}     = 146.6 0.0
  
 
Chemical Shift
 
Chemical Shift
   PREC        = Normal    # nice
+
   {{TAGBL|PREC}}         = Normal    # nice
   ENCUT        = 400.0      # typically higher cutoffs than usual are needed
+
   {{TAGBL|ENCUT}}       = 400.0      # typically higher cutoffs than usual are needed
   ISMEAR = 0; SIGMA= 0.1 # no fancy smearings, SIGMA sufficiently small
+
   {{TAGBL|ISMEAR}} = 0; SIGMA= 0.1 # no fancy smearings, SIGMA sufficiently small
   EDIFF        = 1E-9      # you'd need much smaller EDIFFs.
+
   {{TAGBL|EDIFF}}       = 1E-9      # you'd need much smaller EDIFFs.
 +
  {{TAGBL|LCHIMAG}}      = .TRUE.  # to switch on linear response for chemical shifts
 +
  {{TAGBL|DQ}}          = 0.001        # often the default is sufficient
 +
  {{TAGBL|ICHIBARE}}    = 1      # often the default is sufficient
 +
  {{TAGBL|LNMR_SYM_RED}} = .TRUE. # be on the safe side
 +
  {{TAGBL|NLSPLINE}}    = .TRUE.  # only needed if LREAL is NOT set.
 +
  {{TAGBL|LREAL}}        = A          # helps for speed for large systems, not needed
 +
  {{TAGBL|NBANDS}}      = 25      # to safe memory, ??? = NELECT/2
  
  LCHIMAG      = .TRUE.  # to switch on linear response for chemical shifts
 
  DQ          = 0.001        # often the default is sufficient
 
  ICHIBARE    = 1      # often the default is sufficient
 
  LNMR_SYM_RED = .TRUE. # be on the safe side
 
  NLSPLINE    = .TRUE.  # only needed if LREAL is NOT set.
 
  LREAL        = A          # helps for speed for large systems, not needed
 
  NBANDS      = 25      # to safe memory, ??? = NELECT/2
 
</pre>
 
  
*KPOINTS
+
*{{TAG|KPOINTS}}
 
<pre>
 
<pre>
 
automatic mesh
 
automatic mesh
Line 78: Line 74:
 
</pre>
 
</pre>
  
*POSCAR
+
*{{TAG|POSCAR}}
 
<pre>
 
<pre>
 
Al1 F3
 
Al1 F3
Line 97: Line 93:
 
     0.750000000        0.822499990        0.750000000
 
     0.750000000        0.822499990        0.750000000
 
</pre>
 
</pre>
 
== Used INCAR Tags ==
 
{{DQ}},{{TAG|EDIFF}},{{TAG|EDIFFG}},{{TAG|EMAX}},{{TAG|EMIN}},{{TAG|ENCUT}},{{TAG|GGA}},{{TAG|IALGO}},{{TAG|IBRION}},{{TAG|ICHARG}},{{TAG|ICHIBARE}},{{TAG|INIWAV}},{{TAG|ISIF}},{{TAG|ISMEAR}},{{TAG|ISPIN}},{{TAG|ISTART}},{{TAG|ISYM}},{{TAG|LCHIMAG}},{{TAG|LEFG}},{{TAG|LNMR_SYM_RED}},{{TAG|LREAL}},{{TAG|LWAVE}},{{TAG|NBANDS}},{{TAG|NEDOS}},{{TAG|NLSPLINE}},{{TAG|NSW}},{{TAG|POTIM}},{{TAG|PREC}},{{TAG|QUAD_EFG}},{{TAG|SYSTEM}}
 
  
 
== Download ==
 
== Download ==
[http://www.vasp.at/vasp-workshop/examples/AlF3_NMR.tgz AlF3_NMR.tgz]
+
[[Media:AlF3_NMR.tgz| AlF3_NMR.tgz]]
 
----
 
----
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]
 
  
 
[[Category:Examples]]
 
[[Category:Examples]]

Latest revision as of 13:15, 14 November 2019

Exercise : Determine the 27Al Cq value and the Al and F shieldings.

α-AlF3 crystallizes in the trigonal R -3c space group.

a = b = 4.9305 Å; c = 12.4462 Å

α = β = 90°; γ = 120°

The unit cell contains two independent atoms (1 Al and 1 F) with 6 formula units (AlF3) per unit cell (Z=6). AlF6 octahedron units are linked together by corner sharing. As the conventional unit cell is non-primitive, the primitive rhombohedral one is used for the calculation. It saves a lot of computational time !

We suggest you to use vesta for generation the POSCAR file from the AlF3.cif file. In the standard export procedure, the POSCAR file is generated with the conventional unit cell (non primitive R-cell with 24 atoms inside). Ask VESTA to reduce to unit cell to the primitive one. You will then have only 8 atoms in the POSCAR file.

In this exercise one wants first to calculate the EFG tensor components of 27Al. This is very fast task calculated at the end of the first SCF calculation (ground state property). The experimental values for the Cq is 0.21 MHz. The nuclear quadrupolar momentum used to transform EFG in Cq is Q = 14.66 10-30 m2 (see the paper of Sadoc et al. (http://www.sciencedirect.com/science/article/pii/S0926204014000022) (Flurine has a 1/2 nuclear spin, so Q is zero)

In a second step one wants to calculate the shielding parameters for Al and F. This is done using the linear response using the GIPAW formalism. As the calculation is quite time consuming, only very few k-points and small ENCUT are used with standard PAW data sets. The calculated shielding tensors components can be compared to the ones obtained by Sadoc et al.


 SYSTEM       =  Al F3
 GGA          = PE
 ISTART       = 1
 ICHARG       = 0
 INIWAV       = 1
 LREAL        =  AUTO
 ISYM         = 2
 ISPIN        = 1

Ionic minimisation

 NSW          = 0
 ISIF         = 2
 IBRION       = 2
  1. EDIFFG = -2E-2
 POTIM        = 0.1

Electronic minimisation

 IALGO        = 38
 LWAVE        = .TRUE.
 EMIN         =   -20.0
 EMAX         =   10.0
 NEDOS        = 1601

EFG Calculation

 LEFG         = .TRUE.
 QUAD_EFG     = 146.6 0.0

Chemical Shift

 PREC         = Normal    # nice
 ENCUT        = 400.0      # typically higher cutoffs than usual are needed
 ISMEAR = 0; SIGMA= 0.1 # no fancy smearings, SIGMA sufficiently small
 EDIFF        = 1E-9      # you'd need much smaller EDIFFs.
 LCHIMAG      = .TRUE.   # to switch on linear response for chemical shifts
 DQ           = 0.001         # often the default is sufficient
 ICHIBARE     = 1       # often the default is sufficient
 LNMR_SYM_RED = .TRUE. # be on the safe side
 NLSPLINE     = .TRUE.  # only needed if LREAL is NOT set.
 LREAL        = A          # helps for speed for large systems, not needed
 NBANDS       = 25       # to safe memory, ??? = NELECT/2


automatic mesh
0
Auto
20
Al1 F3
1.0
        4.9305000305         0.0000000000         0.0000000000
        2.4652500153         4.2699382798         0.0000000000
        2.4652650832         1.4233214594         4.1486879977
   Al    F
    2    6
Direct
     0.000000000         0.500000000         0.000000000
     0.500000000         0.000000000         0.500000000
     0.177499995         0.250000000         0.750000000
     0.822499990         0.750000000         0.250000000
     0.677500010         0.322499990         0.250000000
     0.322499990         0.677500010         0.750000000
     0.250000000         0.177499995         0.250000000
     0.750000000         0.822499990         0.750000000

Download

AlF3_NMR.tgz