Re: [Wien] Mixer surprise when using PBE0 hybrid on-site functional
Dear Laurence Thank you so much for your detailled replies. I agree that something curious happens here. In particular, my surprise is why the convergency is fast and leads to a ferromagnetic solution in GGA+U and not in PBE0 on-site hybrid. These two schemes must be quite similar in the way they correct the GGA eigenvalues. I will continue to test the different options of mixer. Just one question, I didn't know the :MV keyword. Where should I find it? Best Regards Xavier Le 20/01/2017 à 22:16, Laurence Marks a écrit : I can provide some partial responses, although there are also some things that I don't understand. Some of this (maybe most) is not the mixer but in other parts of Wien2k. First, the old (2008) version is there if you use MSEC1, but I have not tested it and it may fail. Better is to use MSEC3 which is almost the old version. For some classes of problems this is more stable than MSR1, and works better. If you are talking about the pre-multisecant version (BROYD) that vanished some time ago. Second, there is a nasty "feature" particularly for +U (eece) cases, which is partially discussed in the mixer Readme. There is no guarantee that a solution exists -- the KS theorem is for densities but U is an orbital term. It is very possible to have cases where there is no fixed-point solution. The older MSEC1 (maybe BROYD) could find a fake solution where the density was consistent but the orbital potential was not. The latest version is much better in avoiding them and going for "real" solutions rather than being trapped. For orbital potentials it is very important to look at :MV to check that one really has a self-consistent orbital potential. Third, there are cases where PBE (and all the GGA's in Wien2k that I have tested) give unphysical results when applied to isolated d or f electrons as done for -eece. I guess that the GGA functionals were not designed for the densities of just high L orbitals. This leads to very bad behavior of the mixing. I know of no way to solve this in the mixer, it is a structural problem. It goes away if LDA is used as the form for VXC in -eece. Fourth, larger problem with low symmetry (P1 in particular) can certainly behave badly. Part of this might be "somewhere" in Wien2k coding, part of it is generic to a low symmetry problem. In many cases these have small eigenvalues in the mixing Jacobian which are removed when symmetry is imposed. All one can do is use MSEC3 or some of the additional flags (see the mixer README) such as "SLOW". Fifth...probably exists, but I can't think of it immediately. On Fri, Jan 20, 2017 at 2:03 PM, Xavier Rocquefelte> wrote: Dear Colleagues I did recently a calculation which has been published long time ago using a old WIEN2k version (in 2008). It corresponds to a spin-polarized calculation for the compound CuO. The symmetry is removed and the idea is to estimate the total energies for different magnetic orders to extract magnetic couplings from a mapping analysis. Such calculations were converging fastly without any trouble in 2008. Here I have started from the scratch with a case.cif file to generate the case.struct file and initializing the calculation in a standard manner. Then I wanted to have the energy related to a ferromagnetic situation (not the more stable). I have 8 copper sites in the unit cell I am using. When this calculation is done using PBE+U everything goes fine. However when PBE0 hybrid on-site functional is used we observed oscillations and the magnetic moment disappear, which is definitely not correct. It should be mentionned that the convergency is really bad. If we do a similar calculation on the cristallographic unit cell (2 copper sites only) the calculations converge both in PBE+U and PBE0. The convergency problems only arises for low-symmetry and high number of magnetic elements. I didn't have such problems before and I wonder if we could still use old mixer scheme in such situations. Looking at the userguide, it seems that the mixer does not allow to do as before and PRATT mixer is too slow. Did you encounter similar difficulties (which were not in older WIEN2k versions)? Best Regards Xavier Here is the case.struct: blebleble P LATTICE,NONEQUIV.ATOMS: 16 1_P1 MODE OF CALC=RELA unit=bohr 14.167163 6.46 11.993298 90.00 95.267000 90.00 ATOM -1: X=0.8750 Y=0.7500 Z=0.8750 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -2: X=0.1250 Y=0.2500
Re: [Wien] Mixer surprise when using PBE0 hybrid on-site functional
N.B., in the 16 version if you reduce the GREED to 0.1 it does what people think reducing the mixing factor does (in the unwritten literature). It does not do it the way people think, this there are many misconceptions in the literature about mixing. The latest version does this by turning on a set of internal switches such as SLOW so it is less greedy. This may help with your problem. On Fri, Jan 20, 2017 at 3:16 PM, Laurence Markswrote: > I can provide some partial responses, although there are also some things > that I don't understand. Some of this (maybe most) is not the mixer but in > other parts of Wien2k. > > First, the old (2008) version is there if you use MSEC1, but I have not > tested it and it may fail. Better is to use MSEC3 which is almost the old > version. For some classes of problems this is more stable than MSR1, and > works better. If you are talking about the pre-multisecant version (BROYD) > that vanished some time ago. > > Second, there is a nasty "feature" particularly for +U (eece) cases, which > is partially discussed in the mixer Readme. There is no guarantee that a > solution exists -- the KS theorem is for densities but U is an orbital > term. It is very possible to have cases where there is no fixed-point > solution. The older MSEC1 (maybe BROYD) could find a fake solution where > the density was consistent but the orbital potential was not. The latest > version is much better in avoiding them and going for "real" solutions > rather than being trapped. For orbital potentials it is very important to > look at :MV to check that one really has a self-consistent orbital > potential. > > Third, there are cases where PBE (and all the GGA's in Wien2k that I have > tested) give unphysical results when applied to isolated d or f electrons > as done for -eece. I guess that the GGA functionals were not designed for > the densities of just high L orbitals. This leads to very bad behavior of > the mixing. I know of no way to solve this in the mixer, it is a structural > problem. It goes away if LDA is used as the form for VXC in -eece. > > Fourth, larger problem with low symmetry (P1 in particular) can certainly > behave badly. Part of this might be "somewhere" in Wien2k coding, part of > it is generic to a low symmetry problem. In many cases these have small > eigenvalues in the mixing Jacobian which are removed when symmetry is > imposed. All one can do is use MSEC3 or some of the additional flags (see > the mixer README) such as "SLOW". > > Fifth...probably exists, but I can't think of it immediately. > > On Fri, Jan 20, 2017 at 2:03 PM, Xavier Rocquefelte < > xavier.rocquefe...@univ-rennes1.fr> wrote: > >> Dear Colleagues >> >> I did recently a calculation which has been published long time ago >> using a old WIEN2k version (in 2008). >> >> It corresponds to a spin-polarized calculation for the compound CuO. The >> symmetry is removed and the idea is to estimate the total energies for >> different magnetic orders to extract magnetic couplings from a mapping >> analysis. Such calculations were converging fastly without any trouble >> in 2008. >> >> Here I have started from the scratch with a case.cif file to generate >> the case.struct file and initializing the calculation in a standard >> manner. >> >> Then I wanted to have the energy related to a ferromagnetic situation >> (not the more stable). I have 8 copper sites in the unit cell I am using. >> >> When this calculation is done using PBE+U everything goes fine. However >> when PBE0 hybrid on-site functional is used we observed oscillations and >> the magnetic moment disappear, which is definitely not correct. It >> should be mentionned that the convergency is really bad. If we do a >> similar calculation on the cristallographic unit cell (2 copper sites >> only) the calculations converge both in PBE+U and PBE0. >> >> The convergency problems only arises for low-symmetry and high number of >> magnetic elements. I didn't have such problems before and I wonder if we >> could still use old mixer scheme in such situations. Looking at the >> userguide, it seems that the mixer does not allow to do as before and >> PRATT mixer is too slow. >> >> Did you encounter similar difficulties (which were not in older WIEN2k >> versions)? >> >> Best Regards >> >> Xavier >> >> Here is the case.struct: >> >> blebleble >> P LATTICE,NONEQUIV.ATOMS: 16 1_P1 >> MODE OF CALC=RELA unit=bohr >> 14.167163 6.46 11.993298 90.00 95.267000 90.00 >> ATOM -1: X=0.8750 Y=0.7500 Z=0.8750 >>MULT= 1 ISPLIT= 8 >> Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 >> LOCAL ROT MATRIX:1.000 0.000 0.000 >> 0.000 1.000 0.000 >> 0.000 0.000 1.000 >> ATOM -2: X=0.1250 Y=0.2500 Z=0.6250 >>MULT= 1 ISPLIT= 8 >> Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0
Re: [Wien] Mixer surprise when using PBE0 hybrid on-site functional
I can provide some partial responses, although there are also some things that I don't understand. Some of this (maybe most) is not the mixer but in other parts of Wien2k. First, the old (2008) version is there if you use MSEC1, but I have not tested it and it may fail. Better is to use MSEC3 which is almost the old version. For some classes of problems this is more stable than MSR1, and works better. If you are talking about the pre-multisecant version (BROYD) that vanished some time ago. Second, there is a nasty "feature" particularly for +U (eece) cases, which is partially discussed in the mixer Readme. There is no guarantee that a solution exists -- the KS theorem is for densities but U is an orbital term. It is very possible to have cases where there is no fixed-point solution. The older MSEC1 (maybe BROYD) could find a fake solution where the density was consistent but the orbital potential was not. The latest version is much better in avoiding them and going for "real" solutions rather than being trapped. For orbital potentials it is very important to look at :MV to check that one really has a self-consistent orbital potential. Third, there are cases where PBE (and all the GGA's in Wien2k that I have tested) give unphysical results when applied to isolated d or f electrons as done for -eece. I guess that the GGA functionals were not designed for the densities of just high L orbitals. This leads to very bad behavior of the mixing. I know of no way to solve this in the mixer, it is a structural problem. It goes away if LDA is used as the form for VXC in -eece. Fourth, larger problem with low symmetry (P1 in particular) can certainly behave badly. Part of this might be "somewhere" in Wien2k coding, part of it is generic to a low symmetry problem. In many cases these have small eigenvalues in the mixing Jacobian which are removed when symmetry is imposed. All one can do is use MSEC3 or some of the additional flags (see the mixer README) such as "SLOW". Fifth...probably exists, but I can't think of it immediately. On Fri, Jan 20, 2017 at 2:03 PM, Xavier Rocquefelte < xavier.rocquefe...@univ-rennes1.fr> wrote: > Dear Colleagues > > I did recently a calculation which has been published long time ago > using a old WIEN2k version (in 2008). > > It corresponds to a spin-polarized calculation for the compound CuO. The > symmetry is removed and the idea is to estimate the total energies for > different magnetic orders to extract magnetic couplings from a mapping > analysis. Such calculations were converging fastly without any trouble > in 2008. > > Here I have started from the scratch with a case.cif file to generate > the case.struct file and initializing the calculation in a standard manner. > > Then I wanted to have the energy related to a ferromagnetic situation > (not the more stable). I have 8 copper sites in the unit cell I am using. > > When this calculation is done using PBE+U everything goes fine. However > when PBE0 hybrid on-site functional is used we observed oscillations and > the magnetic moment disappear, which is definitely not correct. It > should be mentionned that the convergency is really bad. If we do a > similar calculation on the cristallographic unit cell (2 copper sites > only) the calculations converge both in PBE+U and PBE0. > > The convergency problems only arises for low-symmetry and high number of > magnetic elements. I didn't have such problems before and I wonder if we > could still use old mixer scheme in such situations. Looking at the > userguide, it seems that the mixer does not allow to do as before and > PRATT mixer is too slow. > > Did you encounter similar difficulties (which were not in older WIEN2k > versions)? > > Best Regards > > Xavier > > Here is the case.struct: > > blebleble > P LATTICE,NONEQUIV.ATOMS: 16 1_P1 > MODE OF CALC=RELA unit=bohr > 14.167163 6.46 11.993298 90.00 95.267000 90.00 > ATOM -1: X=0.8750 Y=0.7500 Z=0.8750 >MULT= 1 ISPLIT= 8 > Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 > LOCAL ROT MATRIX:1.000 0.000 0.000 > 0.000 1.000 0.000 > 0.000 0.000 1.000 > ATOM -2: X=0.1250 Y=0.2500 Z=0.6250 >MULT= 1 ISPLIT= 8 > Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 > LOCAL ROT MATRIX:1.000 0.000 0.000 > 0.000 1.000 0.000 > 0.000 0.000 1.000 > ATOM -3: X=0.1250 Y=0.2500 Z=0.1250 >MULT= 1 ISPLIT= 8 > Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 > LOCAL ROT MATRIX:1.000 0.000 0.000 > 0.000 1.000 0.000 > 0.000 0.000 1.000 > ATOM -4: X=0.8750 Y=0.7500 Z=0.3750 >MULT= 1 ISPLIT= 8 > Cu NPT= 781
[Wien] Mixer surprise when using PBE0 hybrid on-site functional
Dear Colleagues I did recently a calculation which has been published long time ago using a old WIEN2k version (in 2008). It corresponds to a spin-polarized calculation for the compound CuO. The symmetry is removed and the idea is to estimate the total energies for different magnetic orders to extract magnetic couplings from a mapping analysis. Such calculations were converging fastly without any trouble in 2008. Here I have started from the scratch with a case.cif file to generate the case.struct file and initializing the calculation in a standard manner. Then I wanted to have the energy related to a ferromagnetic situation (not the more stable). I have 8 copper sites in the unit cell I am using. When this calculation is done using PBE+U everything goes fine. However when PBE0 hybrid on-site functional is used we observed oscillations and the magnetic moment disappear, which is definitely not correct. It should be mentionned that the convergency is really bad. If we do a similar calculation on the cristallographic unit cell (2 copper sites only) the calculations converge both in PBE+U and PBE0. The convergency problems only arises for low-symmetry and high number of magnetic elements. I didn't have such problems before and I wonder if we could still use old mixer scheme in such situations. Looking at the userguide, it seems that the mixer does not allow to do as before and PRATT mixer is too slow. Did you encounter similar difficulties (which were not in older WIEN2k versions)? Best Regards Xavier Here is the case.struct: blebleble P LATTICE,NONEQUIV.ATOMS: 16 1_P1 MODE OF CALC=RELA unit=bohr 14.167163 6.46 11.993298 90.00 95.267000 90.00 ATOM -1: X=0.8750 Y=0.7500 Z=0.8750 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -2: X=0.1250 Y=0.2500 Z=0.6250 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -3: X=0.1250 Y=0.2500 Z=0.1250 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -4: X=0.8750 Y=0.7500 Z=0.3750 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -5: X=0.6250 Y=0.2500 Z=0.6250 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -6: X=0.3750 Y=0.7500 Z=0.8750 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -7: X=0.3750 Y=0.7500 Z=0.3750 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -8: X=0.6250 Y=0.2500 Z=0.1250 MULT= 1 ISPLIT= 8 Cu NPT= 781 R0=0.5000 RMT=1.9700 Z: 29.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -9: X=0.8750 Y=0.4184 Z=0.6250 MULT= 1 ISPLIT= 8 O NPT= 781 R0=0.0001 RMT=1.6900 Z: 8.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -10: X=0.1250 Y=0.9184 Z=0.8750 MULT= 1 ISPLIT= 8 O NPT= 781 R0=0.0001 RMT=1.6900 Z: 8.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 1.000 ATOM -11: X=0.1250 Y=0.5816 Z=0.3750 MULT= 1 ISPLIT= 8 O NPT= 781 R0=0.0001 RMT=1.6900 Z: 8.0 LOCAL ROT MATRIX:1.000 0.000 0.000 0.000 1.000 0.000 0.000