Hi All,
I am attempting to calculate the phonons for U₃Si₂ using the GGA (PBEsol)+U functional. The optimized lattice constants with U=1.7 are:
a = b = 7.295 Å
c = 3.857 Å,
which is in comparison to experimental data:
a = b = 7.315 Å
c = 3.893 Å.
Below, I have provided the INCAR, POSCAR-unitcell files, and KPOINTS that I used for the calculations at the end of this message.
For the phonon calculations, I employed a 2x2x4 supercell with five displacements generated by the Phonopy code. However, the calculations are not converging. I attempted changing ALGO = Normal to ALGO = VeryFast and ISMEAR = 2 to ISMEAR = 3. I also increased NELM to 150, but these adjustments did not resolve the issue.
The total drift forces for the atomic displacements vary significantly from one displacement to another. For example:
For displacements 1 and 2, the total drift force is < 1e-4 eV/Å,
For displacement 3 and 5, it is around 1e-2 eV/Å,
For displacement 4, it is approximately 1e-3 eV/Å.
Additionally, I encountered the following warning messages:
WARNING in EDDRMM: call to ZHEGV failed, returncode = 6 3 79. and
This one also
-----------------------------------------------------------------------------
| |
| W W AA RRRRR N N II N N GGGG !!! |
| W W A A R R NN N II NN N G G !!! |
| W W A A R R N N N II N N N G !!! |
| W WW W AAAAAA RRRRR N N N II N N N G GGG ! |
| WW WW A A R R N NN II N NN G G |
| W W A A R R N N II N N GGGG !!! |
| |
| The electronic self-consistency was not achieved in the given |
| number of steps (NELM). The forces and other quantities evaluated |
| might not be reliable so examine the results carefully. If you find |
| spurious results, we suggest increasing NELM, if you were close to |
| convergence or switching to a different ALGO or adjusting the |
| density mixing parameters otherwise. |
| |
-----------------------------------------------------------------------------
INCAR
# SCF input for VASP
# Note that VASP uses the FIRST occurence of a keyword
SYSTEM = U3Si2_Force calculations
PREC = Accurate
# ENCUT = 400
IBRION = -1
NSW = 0 ! changed from 100
ISIF = 2
ALGO = VeryFast !Normal (blocked Davidson)
NELM = 150
NELMIN = 2
EDIFF = 1.0e-06 ! was 1e-5
EDIFFG = -0.001
VOSKOWN = 1
NBLOCK = 1
ISPIN = 2
GGA = PS #PBEsol
LDAU = .TRUE.
LDAUTYPE = 2 # 2: simplified rotationally invariant (U_J): Dudarev et al
LDAUL = 3 -1 #l-quantum number, -1 means no on-site interaction is added
LDAUU = 1.7 0 # Effective on-site Coulomb Interactions (eV)
LDAUJ = 0 0 # Effective on-site exchange Interactions (eV)
LDAUPRINT = 0 # 1 write the spin-up and spin down matrix to OUTCAR
LMAXMIX = 6 # 4 for d-elements, 6 for f-elements
INIWAV = 1
ISTART = 0
ICHARG = 2
LWAVE = .FALSE.
LCHARG = .FALSE.
ADDGRID = .FALSE.
ISMEAR = 3 ! was 2 was 1
SIGMA = 0.2
LREAL = .FALSE.
NCORE = 4 ! # of nodes
KPAR = 2 ! mpi-rank =16 , NKPOINTS =32 ==> 2 groups, each kpoint on 8 cores
POSCAR-unitcell
U3Si2
1.000000000000000
5.8984426312529790 4.2918888570923786 -0.0195012428659402
-4.2918888270434019 5.8981701645018036 -0.0599561637662552
-0.0103135917650089 0.0316970283885453 3.8564718251165897
U Si
6 4
Direct
0.1854642126921195 0.6854642126921189 0.5000000000000000
0.8145357873078811 0.3145357873078805 0.5000000000000000
0.3145357873078805 0.1854642126921195 0.5000000000000000
0.6854642126921189 0.8145357873078811 0.5000000000000000
0.0000000000000000 0.0000000000000000 -0.0000000000000000
0.5000000000000000 0.5000000000000000 -0.0000000000000000
0.3858851229787523 0.8858851229787528 -0.0000000000000000
0.6141148770212472 0.1141148770212475 0.0000000000000000
0.1141148770212475 0.3858851229787523 -0.0000000000000000
0.8858851229787528 0.6141148770212472 0.0000000000000000
KPOINTS
Automatic mesh
0
Monkhorst Pack
4 4 4
0. 0. 0.
Thank you in advance for your suggestions!
Iyad
