UT theoretical chemistry code forum

Going to perform NEB for MXene, but back to basic question like from where should I get this POSCAR.IS file, is the base file I define or from the CONTCAR after optimization or from CONTCAR of SCF and what is POSCAR>FS file CONTCAR OF SCF or CONTCAR of Band structure? Which one should I consider

Yes, that's right, the initial structure should be from an optimized CONTCAR from a geometry in your initial state. The final structure should be a CONTCAR from an optimized calculation of your final state. I don't understand the difference between SCF and Band structure - these optimization calculations should converge the geometry, but of course to do that you have to also optimize the band structure and this is done via an SCF calculation.

Thank you Graeme, I've done the optimization of the structure Ti2CO2_CO2, so consider the CONTCAR --> as POSCAR.IS and
secondly I've done my Self consistent field (SCF) calculation and then copied the CONTCAR to POSCAR for Band Structure calculation. so to consider POSCAR.FS which one should I consider? the CONTCAR of Band structure or the CONSTCAR of SCF

I'm not getting the POSCAR.FS to use the nebmake.pl POSCAR.IS POSCAR.FS 5

Please guide me to get the POSCAR.FS

Again, you are always doing SCF calculations to determine the energy and force; with those, you can optimize the structure. It doesn't make any sense (to me) to talk about "secondly doing an SCF calculation". But then, once you have your initial state, you need to determine to what state you want to calculation a reaction to - you are the one who needs to determine the final state that you are interested in.