Effect of tight convergence on band gap
Posted: Mon Jun 03, 2013 8:13 am
Dear sir,
I make my incar file for geometry optimisation of a one dimensional polymer like this:
SYSTEM=POLYMER
PREC=Normal
IBRION=2
EDIFF=1.0e-06
EDIFFG=1.0e-05
INIWAV=1
ISTART=0
ICHARG=2
After that I submit the job for band structure by using the CHGCAR CONTCAR file and perform a self-consistent run using 10 KPOINTS in line mode in direction of polymer extension.
I get the almost correct value of band gap. but the dE value in OSZICAR file was gone only upto 0.392E-02 whereas I had given the value of EDIFFG 1E-05.
To correct this problem, I use the incar file with NSW=200 & ISMEAR=0 AND NSW=200 & ISMEAR=1 respectively in two different jobs to see the results.
the value of dE goes to E-05. But the band gap is incorrect in both cases.
I am finding difficulty to understand the reason for this.
Is tight convergence bother the band gap or there is any other mistake.
Please guide me.
I make my incar file for geometry optimisation of a one dimensional polymer like this:
SYSTEM=POLYMER
PREC=Normal
IBRION=2
EDIFF=1.0e-06
EDIFFG=1.0e-05
INIWAV=1
ISTART=0
ICHARG=2
After that I submit the job for band structure by using the CHGCAR CONTCAR file and perform a self-consistent run using 10 KPOINTS in line mode in direction of polymer extension.
I get the almost correct value of band gap. but the dE value in OSZICAR file was gone only upto 0.392E-02 whereas I had given the value of EDIFFG 1E-05.
To correct this problem, I use the incar file with NSW=200 & ISMEAR=0 AND NSW=200 & ISMEAR=1 respectively in two different jobs to see the results.
the value of dE goes to E-05. But the band gap is incorrect in both cases.
I am finding difficulty to understand the reason for this.
Is tight convergence bother the band gap or there is any other mistake.
Please guide me.