CRPA of SrVO3: Difference between revisions

Latest revision as of 08:50, 13 June 2024

Overview > bandgap of Si in GW > bandstructure of Si in GW (VASP2WANNIER90) > bandstructure of SrVO3 in GW > CRPA of SrVO3 > Equilibrium volume of Si in the RPA > List of tutorials

The following tutorial describes how to perform CRPA calculations, which is available as of VASP 6.

Task

Calculation of the Coulomb matrix elements $U_{ijkl}(\omega=0)$ in the constrained Random Phase Approximation (CRPA) of SrVO₃ between the Vanadium t_2g states.

Performing a CRPA calculation with VASP is a 3-step procedure: a DFT groundstate calculation, a calculation to obtain a number of virtual orbitals, and the actual CRPA calculation itself.

N.B.: This example involves quite a number of individual calculations. The easiest way to run this example is to execute:

./doall.sh

In any case, one can consider the doall.sh script to be an overview of the steps described below.

DFT groundstate calculation

The first step is a conventional DFT (in this case PBE) groundstate calculation.

INCAR (see INCAR.DFT)

SYSTEM  = SrVO3    # system name
NBANDS = 36        # small number  of bands
ISMEAR = 0         # Gaussian smearing
EDIFF = 1E-8       # high precision for groundstate calculation
KPAR = 2           # parallelization of k-points in two groups

Copy the aforementioned file to INCAR:

cp INCAR.DFT INCAR

The POSCAR file describes the structure of the system:

POSCAR

SrVO3
3.84652  #cubic fit for 6x6x6 k-points
 +1.0000000000  +0.0000000000  +0.0000000000 
 +0.0000000000  +1.0000000000  +0.0000000000 
 +0.0000000000  +0.0000000000  +1.0000000000 
Sr V O
 1 1 3
Direct
 +0.0000000000  +0.0000000000  +0.0000000000 
 +0.5000000000  +0.5000000000  +0.5000000000 
 +0.5000000000  +0.5000000000  +0.0000000000 
 +0.5000000000  +0.0000000000  +0.5000000000 
 +0.0000000000  +0.5000000000  +0.5000000000

This file remains unchanged in the following.

The KPOINTS file describes how the first Brillouin zone is sampled. In the first step we use a uniform k-point sampling:

KPOINTS

Automatically generated mesh
 0
Gamma
 4 4 4
 0 0 0

Mind: this is definitely not dense enough for a high-quality description of SrVO₃, but in the interest of speed we will live with it.

Run VASP. If all went well, one should obtain a WAVECAR file containing the PBE wavefunction.

Obtain DFT virtual orbitals and long-wave limit

Use following INCAR file to increase the number of virtual states and to determine the long-wave limit of the polarizability (stored in WAVEDER):

INCAR (see INCAR.PBE)

SYSTEM = SrVO3     # system name
ISMEAR = 0         # Gaussian smearing
KPAR = 2           # parallelization of k-points in two groups
ALGO = Exact       # exact diagonalization
NELM = 1           # one electronic step suffices, since WAVECAR from previous step is present
NBANDS = 96        # need for a lot of bands in GW
LOPTICS = .TRUE.   # we need d phi/ d k  for GW calculations for long-wave limit

Restart VASP. At this stage it is a good idea to make a safety copy of the WAVECAR and WAVEDER files since we will repeatedly need them in the calculations that follow:

cp WAVECAR WAVECAR.PBE
cp WAVEDER WAVEDER.PBE

CRPA Calculation

Calculate the CRPA interaction parameters for the t2g states by using the PBE wavefunction as input

cp WAVECAR.PBE WAVECAR
cp WAVEDER.PBE WAVEDER

And use following input file as

INCAR (see INCAR.CRPA) and run vasp

SYSTEM = SrVO3            # system name
ISMEAR = 0                # Gaussian smearing
NCSHMEM = 1               # switch off shared memory for chi
ALGO = CRPA               # Switch on CRPA
NBANDS = 96               # CRPA needs many empty states
PRECFOCK = Fast           # fast mode for FFTs
NTARGET_STATES = 1 2 3    # exclude wannier states 1 - 3 in screening
LWRITE_WANPROJ = .TRUE.   # write wannier projection file

Warning: As of version 6.2.0 run this tutorial successfully by adding following lines to INCAR. For older version copy wannier90.win.CRPA to wannier90.win and omit following lines in INCAR.

NUM_WANN = 3 
WANNIER90_WIN = "
num_bands=   96

# because bands 21, 22, 23 do not cross with other bands
# one can exclude all other bands in wannierization
# and omit the definition of an energy window like so
exclude_bands = 1-20, 24-96

begin projections
 V:dxy;dxz;dyz
end projections
"

The CRPA interaction values for $\omega=0$ can be found in the OUTCAR:

spin components:  1  1, frequency:    0.0000    0.0000

screened Coulomb repulsion U_iijj between MLWFs:
        1         2         3
   1    3.3746    2.3385    2.3385
   2    2.3385    3.3746    2.3385
   3    2.3385    2.3385    3.3746

screened Coulomb repulsion U_ijji between MLWFs:
        1         2         3
   1    3.3746    0.4429    0.4429
   2    0.4429    3.3746    0.4429
   3    0.4429    0.4429    3.3746

screened Coulomb repulsion U_ijij between MLWFs:
        1         2         3
   1    3.3746    0.4429    0.4429
   2    0.4429    3.3746    0.4429
   3    0.4429    0.4429    3.3746 

averaged interaction parameter
screened Hubbard U =    3.3746   -0.0000
screened Hubbard u =    2.3385    0.0000
screened Hubbard J =    0.4429   -0.0000

N.B.: The frequency point

\omega

can be set by OMEGAMAX in the INCAR. For instance to evaluate the CRPA interaction matrix at

\omega=10

eV, add

 OMEGAMAX = 10

to the INCAR and restart VASP. In contrast, adding following two lines to the INCAR

 OMEGAMAX = 10 
 NOMEGAR = 0

tells VASP to calculate the interaction on the imaginary frequency axis at $\omega=i 10$ . This can be used to evaluate $U$ at a specific Matsubara frequency point.

In addition, the bare Coulomb interaction matrix is calculated for a high VCUTOFF and low energy cutoff ENCUTGW and written in that order to the OUTCAR file. Look for the lines similar to:

spin components:  1  1

bare Coulomb repulsion V_iijj between MLWFs:
        1         2         3
   1   16.3485   15.0984   15.0984
   2   15.0984   16.3485   15.0984
   3   15.0984   15.0984   16.3485

bare Coulomb repulsion V_ijji between MLWFs:
        1         2         3
   1   16.3485    0.5351    0.5351
   2    0.5351   16.3485    0.5351
   3    0.5351    0.5351   16.3485

bare Coulomb repulsion V_ijij between MLWFs:
        1         2         3
   1   16.3485    0.5351    0.5351
   2    0.5351   16.3485    0.5351
   3    0.5351    0.5351   16.3485

averaged bare interaction
bare Hubbard U =   16.3485   -0.0000
bare Hubbard u =   15.0984   -0.0000
bare Hubbard J =    0.5351    0.0000

CRPA calculation with spacetime Algorithm

Note that the same frequency grid is used as for ALGO=RPA (RPA correlation energy calculation) and can not be changed directly. To calculate the CRPA interaction for a set of automatically chosen imaginary frequency points use once again the PBE wavefunction as input

cp WAVECAR.PBE WAVECAR
cp WAVEDER.PBE WAVEDER

Currently, this step requires the WANPROJ file from previous step, no wannier90.win file is necessary. You can also, delete WANPROJ and define a wannier projection as in the previous step in the INCAR.

Select the space-time CRPA algorithm with following file:

INCAR (see INCAR.CRPAR)

SYSTEM = SrVO3             # system name
ISMEAR = 0                 # Gaussian smearing
NCSHMEM = 1                # switch off shared memory for chi
ALGO = CRPAR               # Switch on CRPA on imaginary axis
NBANDS = 96                # CRPA needs many empty states
PRECFOCK = Fast            # fast mode for FFTs
NTARGET_STATES = 1 2 3     # exclude wannier states 1 - 3 in screening
NCRPA_BANDS = 21 22 23     # remove bands 21-23 in screening, currently required for space-time algo
NOMEGA = 12                # use 12 imaginary frequency points
NTAUPAR = 4                # distribute 12 time points into 4 groups

Run VASP and make a copy of the output file

cp OUTCAR OUTCAR.CRPAR

After a successful run, the interaction values are written to the OUTCAR file. Here is the result for the first frequency point:

spin components:  1  1, frequency:    0.0000    0.2248

screened Coulomb repulsion U_iijj between MLWFs:
        1         2         3
   1    3.3798    2.3436    2.3436
   2    2.3436    3.3798    2.3436
   3    2.3436    2.3436    3.3798

screened Coulomb repulsion U_ijji between MLWFs:
        1         2         3
   1    3.3798    0.4433    0.4433
   2    0.4433    3.3798    0.4433
   3    0.4433    0.4433    3.3798

screened Coulomb repulsion U_ijij between MLWFs:
        1         2         3
   1    3.3798    0.4433    0.4433
   2    0.4433    3.3798    0.4433
   3    0.4433    0.4433    3.3798

averaged interaction parameter
screened Hubbard U =    3.3798   -0.0000
screened Hubbard u =    2.3436    0.0000
screened Hubbard J =    0.4433   -0.0000

N.B.: The number of frequency points should be large enough to guarantee for an accurate Fourier transformation of the CRPA polarizability matrix from the imaginary time to imaginary frequency domain. See ACFDT/RPA calculations for more information.

Downloads

CRPA_of_SrVO3.zip

Overview > bandgap of Si in GW > bandstructure of Si in GW (VASP2WANNIER90) > bandstructure of SrVO3 in GW > CRPA of SrVO3 > Equilibrium volume of Si in the RPA > List of tutorials

Back to the main page.

@@ Line 1: / Line 1: @@
-{{Template:gw}}
+{{Template:GW - Tutorial}}
+The following tutorial describes how to perform CRPA calculations, which is available as of VASP 6.
 == Task ==
 Calculation of the Coulomb matrix elements <math>U_{ijkl}(\omega=0)</math> in the constrained Random Phase Approximation ([[Constrained Random Phase Approximation|CRPA]]) of SrVO<sub>3</sub> between the Vanadium t<sub>2g</sub> states.
 ----
@@ Line 10: / Line 10: @@
 The easiest way to run this example is to execute:
   ./doall.sh
-And compare the output of the different steps (DFT, GW, HSE) by:
- ./plotall.sh
 In any case, one can consider the <tt>doall.sh</tt> script to be an overview of the steps described below.
@@ Line 21: / Line 18: @@
 *{{TAG|INCAR}} (see INCAR.DFT)
-  {{TAGBL|SYSTEM}}  = SrVO3                        # system name
+  {{TAGBL|SYSTEM}}  = SrVO3    # system name
-  {{TAGBL|NBANDS}} = 36                            # small number  of bands
+  {{TAGBL|NBANDS}} = 36        # small number  of bands
-  {{TAGBL|ISMEAR}} = 0                             # Gaussian smearing
+  {{TAGBL|ISMEAR}} = 0         # Gaussian smearing
-  {{TAGBL|EDIFF}} = 1E-8                           # high precision for groundstate calculation
+  {{TAGBL|EDIFF}} = 1E-8       # high precision for groundstate calculation
-  {{TAGBL|KPAR}} = 2                               # parallelization of k-points in two groups
+  {{TAGBL|KPAR}} = 2           # parallelization of k-points in two groups
 Copy the aforementioned file to {{TAG|INCAR}}:
@@ Line 55: / Line 52: @@
 <pre>
 Automatically generated mesh
 Gamma
 4 4
@@ Line 68: / Line 65: @@
 Use following {{TAG|INCAR}} file to increase the number of virtual states and to determine the long-wave limit of the polarizability (stored in {{TAG|WAVEDER}}):
-*{{TAG|INCAR}} (see INCAR.DIAG)
+*{{TAG|INCAR}} (see INCAR.PBE)
-  {{TAGBL|SYSTEM}} = SrVO3                         # system name
+  {{TAGBL|SYSTEM}} = SrVO3     # system name
-  {{TAGBL|ISMEAR}} = 0                             # Gaussian smearing
+  {{TAGBL|ISMEAR}} = 0         # Gaussian smearing
-  {{TAGBL|KPAR}} = 2                               # parallelization of k-points in two groups
+  {{TAGBL|KPAR}} = 2           # parallelization of k-points in two groups
-  {{TAGBL|ALGO}} = Exact                           # exact diagonalization
+  {{TAGBL|ALGO}} = Exact       # exact diagonalization
-  {{TAGBL|NELM}} = 1                               # one electronic step suffices, since WAVECAR from previous step is present
+  {{TAGBL|NELM}} = 1           # one electronic step suffices, since WAVECAR from previous step is present
-  {{TAGBL|NBANDS}} = 96                            # need for a lot of bands in GW
+  {{TAGBL|NBANDS}} = 96        # need for a lot of bands in GW
-  {{TAGBL|LOPTICS}} = .TRUE.                       # we need d phi/ d k  for GW calculations for long-wave limit
+  {{TAGBL|LOPTICS}} = .TRUE.   # we need d phi/ d k  for GW calculations for long-wave limit
 Restart VASP.
 At this stage it is a good idea to make a safety copy of the {{TAG|WAVECAR}} and {{TAG|WAVEDER}} files since we will repeatedly need them in the calculations that follow:
-  cp {{TAGBL|WAVECAR}} WAVECAR.DIAG
+  cp {{TAGBL|WAVECAR}} WAVECAR.PBE
-  cp {{TAGBL|WAVEDER}} WAVEDER.DIAG
+  cp {{TAGBL|WAVEDER}} WAVEDER.PBE
 == CRPA Calculation ==
 Calculate the CRPA interaction parameters for the t2g states by using the PBE wavefunction as input
-  cp WAVECAR.DIAG {{TAGBL|WAVECAR}}
+  cp WAVECAR.PBE {{TAGBL|WAVECAR}}
-  cp WAVEDER.DIAG {{TAGBL|WAVEDER}}
+  cp WAVEDER.PBE {{TAGBL|WAVEDER}}
-Use following Wannier projection for the basis:
+And use following input file as
+*{{TAG|INCAR}} (see INCAR.CRPA) and run vasp
+ {{TAGBL|SYSTEM}} = SrVO3            # system name
+ {{TAGBL|ISMEAR}} = 0                # Gaussian smearing
+ {{TAGBL|NCSHMEM}} = 1               # switch off shared memory for chi
+ {{TAGBL|ALGO}} = CRPA               # Switch on CRPA
+ {{TAGBL|NBANDS}} = 96               # CRPA needs many empty states
+ {{TAGBL|PRECFOCK}} = Fast           # fast mode for FFTs
+ {{TAGBL|NTARGET_STATES}} = 1 2 3    # exclude wannier states 1 - 3 in screening
+ {{TAGBL|LWRITE_WANPROJ}} = .TRUE.   # write wannier projection file
+{{NB|warning|As of version 6.2.0 run this tutorial successfully by adding following lines to INCAR. For older version copy wannier90.win.CRPA to wannier90.win and omit following lines in INCAR.}}
-*{{TAG|wannier90.win}} (see wannier90.win.CRPA)
+ {{TAGBL|NUM_WANN}} = 3
-  num_wann =    3
+  {{TAGBL|WANNIER90_WIN}} = "
   num_bands=   96
-  # PBE energy window of t2g states (band 21-23)
+  # because bands 21, 22, 23 do not cross with other bands
-  dis_win_min = 6.4
+  # one can exclude all other bands in wannierization
-  dis_win_max = 9.0
+ # and omit the definition of an energy window like so
+  exclude_bands = 1-20, 24-96
   begin projections
    V:dxy;dxz;dyz
   end projections
+  "
-Copy this file to wannier90.win
+The CRPA interaction values for <math>\omega=0</math> can be found in the {{TAG|OUTCAR}}:
- cp wannier90.win.CRPA wannier90.win
-And use following input file as
-*{{TAG|INCAR}} (see INCAR.CRPA)
- {{TAGBL|SYSTEM}} = SrVO3                         # system name
- {{TAGBL|ISMEAR}} = 0                             # Gaussian smearing
- {{TAGBL|NCSHMEM}} = 1                            # switch off shared memory for chi
- {{TAGBL|ALGO}} = CRPA                            # Switch on CRPA
- {{TAGBL|NBANDS}} = 96                            # CRPA needs many empty states
- {{TAGBL|PRECFOCK}} = Fast                        # fast mode for FFTs
- {{TAGBL|NTARGET_STATES}} = 1 2 3                 # exclude wannier states 1 - 3 in screening
-  {{TAGBL|LWRITE_WANPROJ}} = .TRUE.                # write wannier projection file
-and run VASP. The CRPA interaction values for <math>\omega=0</math> can be found in the {{TAG|OUTCAR}}:
   spin components:  1  1, frequency:    0.0000    0.0000
@@ Line 148: / Line 143: @@
    {{TAGBL|NOMEGAR}} = 0
 tells VASP to calculate the interaction on the imaginary frequency axis at <math>\omega=i 10</math>. This can be used to evaluate <math>U</math> at a specific Matsubara frequency point.
+In addition, the bare Coulomb interaction matrix is calculated for a high {{TAG|VCUTOFF}} and low energy cutoff {{TAG|ENCUTGW}} and written in that order to the {{TAG|OUTCAR}} file. Look for the lines similar to:
+ spin components:  1  1
+ bare Coulomb repulsion V_iijj between MLWFs:
+         2         3
+   16.3485   15.0984   15.0984
+   15.0984   16.3485   15.0984
+   15.0984   15.0984   16.3485
+ bare Coulomb repulsion V_ijji between MLWFs:
+         2         3
+   16.3485    0.5351    0.5351
+    0.5351   16.3485    0.5351
+    0.5351    0.5351   16.3485
+ bare Coulomb repulsion V_ijij between MLWFs:
+         2         3
+   16.3485    0.5351    0.5351
+    0.5351   16.3485    0.5351
+    0.5351    0.5351   16.3485
+ averaged bare interaction
+ bare Hubbard U =   16.3485   -0.0000
+ bare Hubbard u =   15.0984   -0.0000
+ bare Hubbard J =    0.5351    0.0000
 === CRPA calculation with spacetime Algorithm ===
 Note that the same frequency grid is used as for {{TAG|ALGO}}=RPA (RPA correlation energy calculation) and can not be changed directly.
 To calculate the CRPA interaction for a set of automatically chosen imaginary frequency points use once again the PBE wavefunction as input
-  cp WAVECAR.DIAG {{TAGBL|WAVECAR}}
+  cp WAVECAR.PBE {{TAGBL|WAVECAR}}
-  cp WAVEDER.DIAG {{TAGBL|WAVEDER}}
+  cp WAVEDER.PBE {{TAGBL|WAVEDER}}
-Currently, this step requires uses the {{TAG|WANPROJ}} file from previous step, no wannier90.win file is necessary.
+Currently, this step requires the {{TAG|WANPROJ}} file from previous step, no wannier90.win file is necessary.
+You can also, delete {{TAG|WANPROJ}} and define a wannier projection as in the previous step in the {{FILE|INCAR}}.
 Select the space-time CRPA algorithm with following file:
 *{{TAG|INCAR}} (see INCAR.CRPAR)
-  {{TAGBL|SYSTEM}} = SrVO3                         # system name
+  {{TAGBL|SYSTEM}} = SrVO3             # system name
-  {{TAGBL|ISMEAR}} = 0                             # Gaussian smearing
+  {{TAGBL|ISMEAR}} = 0                 # Gaussian smearing
-  {{TAGBL|NCSHMEM}} = 1                            # switch off shared memory for chi
+  {{TAGBL|NCSHMEM}} = 1                # switch off shared memory for chi
-  {{TAGBL|ALGO}} = CRPAR                           # Switch on CRPA on imaginary axis
+  {{TAGBL|ALGO}} = CRPAR               # Switch on CRPA on imaginary axis
-  {{TAGBL|NBANDS}} = 96                            # CRPA needs many empty states
+  {{TAGBL|NBANDS}} = 96                # CRPA needs many empty states
-  {{TAGBL|PRECFOCK}} = Fast                        # fast mode for FFTs
+  {{TAGBL|PRECFOCK}} = Fast            # fast mode for FFTs
-  {{TAGBL|NTARGET_STATES}} = 1 2 3                 # exclude wannier states 1 - 3 in screening
+  {{TAGBL|NTARGET_STATES}} = 1 2 3     # exclude wannier states 1 - 3 in screening
-  {{TAGBL|NCRPA_BANDS}} = 21 22 23                 # remove bands 21-23 in screening, currently required for space-time algo
+  {{TAGBL|NCRPA_BANDS}} = 21 22 23     # remove bands 21-23 in screening, currently required for space-time algo
-  {{TAGBL|NOMEGA}} = 12                            # use 12 imaginary frequency points
+  {{TAGBL|NOMEGA}} = 12                # use 12 imaginary frequency points
-  {{TAGBL|NTAUPAR}} = 4                            # distribute 12 time points into 4 groups
+  {{TAGBL|NTAUPAR}} = 4                # distribute 12 time points into 4 groups
 Run VASP and make a copy of the output file
   cp {{TAGBL|OUTCAR}} OUTCAR.CRPAR
-After a successful run, the interaction values are written to the {{TAG|OUTCAR}} file. Here is the result for frequency point No. 9:
+After a successful run, the interaction values are written to the {{TAG|OUTCAR}} file. Here is the result for the first frequency point:
+  spin components:  1  1, frequency:    0.0000    0.2248
-  spin components:  1  1, frequency:    0.0000   29.6555
   screened Coulomb repulsion U_iijj between MLWFs:
          2         3
-  11.0815    9.9315    9.9315
+   3.3798    2.3436    2.3436
-    9.9315   11.0815    9.9315
+    2.3436    3.3798    2.3436
-    9.9315    9.9315   11.0815
+    2.3436    2.3436    3.3798
   screened Coulomb repulsion U_ijji between MLWFs:
          2         3
-  11.0815    0.4994    0.4994
+   3.3798    0.4433    0.4433
-    0.4994   11.0815    0.4994
+    0.4433    3.3798    0.4433
-    0.4994    0.4994   11.0815
+    0.4433    0.4433    3.3798
   screened Coulomb repulsion U_ijij between MLWFs:
          2         3
-  11.0815    0.4994    0.4994
+   3.3798    0.4433    0.4433
-    0.4994   11.0815    0.4994
+    0.4433    3.3798    0.4433
-    0.4994    0.4994   11.0815
+    0.4433    0.4433    3.3798
   averaged interaction parameter
-  screened Hubbard U =   11.0815    0.0000
+  screened Hubbard U =    3.3798   -0.0000
-  screened Hubbard u =    9.9315    0.0000
+  screened Hubbard u =    2.3436    0.0000
-  screened Hubbard J =    0.4994   -0.0000
+  screened Hubbard J =    0.4433   -0.0000
-Note that interactions at high imaginary frequency points approach the bare Coulomb interaction:
+:'''N.B.:''' The number of frequency points should be large enough to guarantee for an accurate Fourier transformation of the CRPA polarizability matrix from the imaginary time to imaginary frequency domain. See [[ACFDT/RPA calculations#Low_scaling_ACFDT.2FRPA_algorithm|ACFDT/RPA calculations]] for more information.
- bare Hubbard U =   16.3485    0.0000
+== Downloads ==
+[[Media:CRPA of SrVO3.zip| CRPA_of_SrVO3.zip]]
-:'''N.B.:''' The number of frequency points should be large enough to guarantee for an accurate Fourier transformation of the CRPA polarizability matrix from the imaginary time to imaginary frequency domain. See [[ACFDT/RPA calculations#Low_scaling_ACFDT.2FRPA_algorithm|ACFDT/RPA calculations]] for more information.
+{{Template:GW - Tutorial}}
-{{Template:gw}}
 Back to the [[The_VASP_Manual|main page]].
-[[Category:Examples]]
+[[Category:Examples]][[Category:Constrained-random-phase approximation]]