I've got some questions concerning fixed spin calculations.
Is it possible to constrain the direction of magnetic moments
without constraining the magnitude |m| of the moments?
And is it also possible to combine constrained moment
and spin spiral calculations? E.g. to simulate magnon spectra
by a using small cone angle for the spin spiral? Examples would be greatly
appreciated, since my previous attempts using "constrained spirals" for iron
hardly converge :(
thanks for the nice support and helpful discussions,
rabbit
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
thanks for the rapid response :), I'm going to test this now.
By the way, why corresponds the magnetic field
bfieldc
-0.01 0.0 -0.01
to the (1,1,1)-direction?
thanks,
rabbit
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi rabbit,
of course you are right it is not the (1,1,1) direction, it is the (1,0,1) as it should be for a conical spiral with teta=45. I put the wrong comment but the right input.
I'm trying this test myself.
Best
Francesco
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I first started a collinear calculation as you suggested, with
tilted magnetic configuration of around 30 degree from z-axis.
bfieldc
0.012 0.0 0.021
Having this collinear groundstate I want to proceed calculating the spirals
having this cone angle.
Unfortunately I have already problems to converge the collinear solution for tilted magnetic field.
Maybe there are some more tricks with the mixing parameter:
Here's my inputfile:
tasks
0
spinpol
.true.
! high accuracy for later spiral calculations
rgkmax
9.0
! also high kpoint-sampling for accuracy
ngridk
16 16 16
Using this input I've problems to converge, so here are the first 80
RMS -steps:
RMS change in effective potential (target) : 38.07574573 ( 0.1000000000E-06)
RMS change in effective potential (target) : 51.89844946 ( 0.1000000000E-06)
RMS change in effective potential (target) : 59.81885349 ( 0.1000000000E-06)
RMS change in effective potential (target) : 61.47818188 ( 0.1000000000E-06)
RMS change in effective potential (target) : 57.75121315 ( 0.1000000000E-06)
RMS change in effective potential (target) : 50.35165257 ( 0.1000000000E-06)
RMS change in effective potential (target) : 41.22365156 ( 0.1000000000E-06)
RMS change in effective potential (target) : 31.98741055 ( 0.1000000000E-06)
RMS change in effective potential (target) : 23.65620170 ( 0.1000000000E-06)
RMS change in effective potential (target) : 16.68702307 ( 0.1000000000E-06)
RMS change in effective potential (target) : 11.17516405 ( 0.1000000000E-06)
RMS change in effective potential (target) : 7.055449239 ( 0.1000000000E-06)
RMS change in effective potential (target) : 4.167917190 ( 0.1000000000E-06)
RMS change in effective potential (target) : 2.293884836 ( 0.1000000000E-06)
RMS change in effective potential (target) : 1.180619032 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5809657310 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2898410979 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1594902782 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9869687293E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6371739731E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4207313552E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2878282037E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2018285649E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1468291178E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1075830726E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7734024655E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5406440740E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3711203723E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2587803413E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1888872089E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1436725552E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1103706467E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.8291419759E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6061008799E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4320085237E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2990260603E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1959001591E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1259785177E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7967111013E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5296479332E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3823366363E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3010690443E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2464693995E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2121635262E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1975187687E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1932730051E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1896918936E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1822786263E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1706500423E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1564319316E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1411059814E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1250014356E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1093056775E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9412273437E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7993612248E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6659618634E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5504756410E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4504960033E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3512693962E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2881500594E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2350757363E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1941427229E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1602577918E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1338895245E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1164385455E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9780687159E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.8466210070E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7704267379E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6950158320E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6453915592E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6235414323E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5906089862E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5550979666E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5410860644E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5209454199E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5444899983E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5281184705E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4972852155E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5032791048E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5076441670E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4904172524E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5170461346E-06 ( 0.1000000000E-06)
As you can see the convergence is quite slow and also not really smooth at the end (its still running). Therefore
I'm a little bit afraid of the 'computational cost' when switching on spin spirals in this case, after
the collinear calculation converges...
Should I therefor decrease the beta0-parameter more?
Ore are there some experience playing with the
betamix-parameter?
Thanks a lot :),
Fritz
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello Fritz,
I would first suggest to use LDA, since the problem with GGA you spotted in your previous post has been fixed by Kay for the next release. Or maybe you have already a version in which this fixed?
Anyhow my experience is that LDA is always less probelmatic than GGA.
Second I would firts converge with big magnetic field, it seems I acn achieve convergence faster and easier if I start from this soultion and then reduce the field. I'm still investigating that, so I'll be glad if you could help me on this.
Something like (theta=30 deg)
--------------
task
0
! LSDA (default)
xctype
3
! big magnetic field mod(b)=3.0
bfieldc
-1.50 0.0 -2.59
! this should be enough
ngridk
12 12 12
! mixing for safety decreased to 0.02
beta0
0.02
---------
and after this
---------
task
1
! decrease magnetic field to mod(b)=0.01
bfieldc
0.05 0.0 0.086
-----------
I'm doing a very similar calculation for theta=25 deg , but with LSDA.
I'm using this input
Dear Exciting users,
I've got some questions concerning fixed spin calculations.
Is it possible to constrain the direction of magnetic moments
without constraining the magnitude |m| of the moments?
And is it also possible to combine constrained moment
and spin spiral calculations? E.g. to simulate magnon spectra
by a using small cone angle for the spin spiral? Examples would be greatly
appreciated, since my previous attempts using "constrained spirals" for iron
hardly converge :(
thanks for the nice support and helpful discussions,
rabbit
Dear Francesco,
thanks for the rapid response :), I'm going to test this now.
By the way, why corresponds the magnetic field
bfieldc
-0.01 0.0 -0.01
to the (1,1,1)-direction?
thanks,
rabbit
Hi rabbit,
of course you are right it is not the (1,1,1) direction, it is the (1,0,1) as it should be for a conical spiral with teta=45. I put the wrong comment but the right input.
I'm trying this test myself.
Best
Francesco
Dear Francesco,
I first started a collinear calculation as you suggested, with
tilted magnetic configuration of around 30 degree from z-axis.
bfieldc
0.012 0.0 0.021
Having this collinear groundstate I want to proceed calculating the spirals
having this cone angle.
Unfortunately I have already problems to converge the collinear solution for tilted magnetic field.
Maybe there are some more tricks with the mixing parameter:
Here's my inputfile:
tasks
0
spinpol
.true.
! high accuracy for later spiral calculations
rgkmax
9.0
gmaxvr
18.0
lmaxapw
16
lmaxvr
10
lmaxmat
10
nempty
20
! convergence: maximum mixing parameter beta0 decreased
beta0
0.05
betamax
1.0
! cone angle around 30 degree
bfieldc
0.012 0.0 0.021
epspot
1.e-7
xctype
20
stype
1
swidth
0.00551
avec
-0.5 0.5 0.5
0.5 -0.5 0.5
0.5 0.5 -0.5
scale
5.404
sppath
''
atoms
1 : nspecies
'Fe.in' : spfname
1 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
! also high kpoint-sampling for accuracy
ngridk
16 16 16
Using this input I've problems to converge, so here are the first 80
RMS -steps:
RMS change in effective potential (target) : 38.07574573 ( 0.1000000000E-06)
RMS change in effective potential (target) : 51.89844946 ( 0.1000000000E-06)
RMS change in effective potential (target) : 59.81885349 ( 0.1000000000E-06)
RMS change in effective potential (target) : 61.47818188 ( 0.1000000000E-06)
RMS change in effective potential (target) : 57.75121315 ( 0.1000000000E-06)
RMS change in effective potential (target) : 50.35165257 ( 0.1000000000E-06)
RMS change in effective potential (target) : 41.22365156 ( 0.1000000000E-06)
RMS change in effective potential (target) : 31.98741055 ( 0.1000000000E-06)
RMS change in effective potential (target) : 23.65620170 ( 0.1000000000E-06)
RMS change in effective potential (target) : 16.68702307 ( 0.1000000000E-06)
RMS change in effective potential (target) : 11.17516405 ( 0.1000000000E-06)
RMS change in effective potential (target) : 7.055449239 ( 0.1000000000E-06)
RMS change in effective potential (target) : 4.167917190 ( 0.1000000000E-06)
RMS change in effective potential (target) : 2.293884836 ( 0.1000000000E-06)
RMS change in effective potential (target) : 1.180619032 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5809657310 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2898410979 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1594902782 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9869687293E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6371739731E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4207313552E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2878282037E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2018285649E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1468291178E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1075830726E-01 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7734024655E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5406440740E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3711203723E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2587803413E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1888872089E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1436725552E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1103706467E-02 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.8291419759E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6061008799E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4320085237E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2990260603E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1959001591E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1259785177E-03 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7967111013E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5296479332E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3823366363E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3010690443E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2464693995E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2121635262E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1975187687E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1932730051E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1896918936E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1822786263E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1706500423E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1564319316E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1411059814E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1250014356E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1093056775E-04 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9412273437E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7993612248E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6659618634E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5504756410E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4504960033E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.3512693962E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2881500594E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.2350757363E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1941427229E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1602577918E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1338895245E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.1164385455E-05 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.9780687159E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.8466210070E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.7704267379E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6950158320E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6453915592E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.6235414323E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5906089862E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5550979666E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5410860644E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5209454199E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5444899983E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5281184705E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4972852155E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5032791048E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5076441670E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.4904172524E-06 ( 0.1000000000E-06)
RMS change in effective potential (target) : 0.5170461346E-06 ( 0.1000000000E-06)
As you can see the convergence is quite slow and also not really smooth at the end (its still running). Therefore
I'm a little bit afraid of the 'computational cost' when switching on spin spirals in this case, after
the collinear calculation converges...
Should I therefor decrease the beta0-parameter more?
Ore are there some experience playing with the
betamix-parameter?
Thanks a lot :),
Fritz
Hello Fritz,
I would first suggest to use LDA, since the problem with GGA you spotted in your previous post has been fixed by Kay for the next release. Or maybe you have already a version in which this fixed?
Anyhow my experience is that LDA is always less probelmatic than GGA.
Second I would firts converge with big magnetic field, it seems I acn achieve convergence faster and easier if I start from this soultion and then reduce the field. I'm still investigating that, so I'll be glad if you could help me on this.
Something like (theta=30 deg)
--------------
task
0
! LSDA (default)
xctype
3
! big magnetic field mod(b)=3.0
bfieldc
-1.50 0.0 -2.59
! this should be enough
ngridk
12 12 12
! mixing for safety decreased to 0.02
beta0
0.02
---------
and after this
---------
task
1
! decrease magnetic field to mod(b)=0.01
bfieldc
0.05 0.0 0.086
-----------
I'm doing a very similar calculation for theta=25 deg , but with LSDA.
I'm using this input
-----------
tasks
0
bfieldc
0.845236523 0.0 1.812615374
atoms
1
'Fe.in' : spfname
1 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
avec
-0.5 0.5 0.5
0.5 -0.5 0.5
0.5 0.5 -0.5
scale
5.423516
spinpol
.true.
autormt
.true.
beta0
0.05
rgkmax
9.0
gmaxvr
18.0
nempty
20
lmaxvr
10
lmaxmat
10
lmaxapw
16
epspot
1.e-7
swidth
0.005
ngridk
12 12 12
vkloff
0.75 0.5 0.25
------------
and after reduced bfieldc to
0.042 0.0 0.090
and converge again.
Let's see if this work and let's keep in touch.
Best
Francesco