My Community

Hi,
I am a user of VASP. When I use this software to do some calculations, I have some problems.
1) Bulk calculation. The system of calculation is LiCoO2, the XRD results of this crystal’s parameters are a=0.28166nm and c=1.408nm. However, the calculation results are a= 0.312nm and c=1.5967nm.The error is more than 10%, it is too big. But I do not know the reason. Please help me.
2) When I calculated the volume minimization of LiCoO2, there is one line on the screen “ ZBRENT: fatal internal in brackting, system-shutdown; contact gK immediately�. What is the matter?
Thanks
Best regards

1) please read the tutorial files accuracy.pdf and option.pdf (http://cms.mpi.univie.ac.at/vasp-workshop) on how to optimize the
structure of a cell.
Mind that the type of XC of the PP you use may also influence the results slightly

2) this means that using Brent's algorithm for searching the next geometry (Numerical recipies, Section 9.3) did not give a reasonable result. Please check whether the ionic relaxations of your calculation are reasonable. If they are not, please have a look whether every ionic step has been converged electronically.
If it has been, change IBRION and/or POTIM