Non-self consistent steps with charged systems
Posted: Wed Jul 07, 2010 4:31 pm
I am using VASP 4.6.31.
My system is a deprotonated acetic acid molecule, i.e. CH3COO-, so I set NELECT=24 in the INCAR file. After the initial non-self-consistent steps however, there is always the message
BRMIX: very serious problems the old and the new charge density differ
old charge density: 23.00000 new 24.00000
since the normal number of valence electrons (i.e. 23 for CH3COO) is used during the non-self-consistent period. Firstly, is this a problem? The difference between the total energy for the acetic acid and the deprotonated acetic acid is very small in my calculations (~2 eV vs. ~15eV when I use Gaussian), and I wonder if this could be the problem. Is there some way to tell VASP to use 24 electrons also during the non-self-consistent steps? Does it even matter that 23 electrons are used initially (if so then then some other problem must be causing the very low value for the deprotonation energy).
One more thing: if I want to run a calculation without any non-self consistent steps, then I set NELMDL=0. When I do this however, I still get five non-self consistent steps. Is something else over-riding the NELMDL flag (I am using ALGO=NORMAL)?
<span class='smallblacktext'>[ Edited ]</span>
My system is a deprotonated acetic acid molecule, i.e. CH3COO-, so I set NELECT=24 in the INCAR file. After the initial non-self-consistent steps however, there is always the message
BRMIX: very serious problems the old and the new charge density differ
old charge density: 23.00000 new 24.00000
since the normal number of valence electrons (i.e. 23 for CH3COO) is used during the non-self-consistent period. Firstly, is this a problem? The difference between the total energy for the acetic acid and the deprotonated acetic acid is very small in my calculations (~2 eV vs. ~15eV when I use Gaussian), and I wonder if this could be the problem. Is there some way to tell VASP to use 24 electrons also during the non-self-consistent steps? Does it even matter that 23 electrons are used initially (if so then then some other problem must be causing the very low value for the deprotonation energy).
One more thing: if I want to run a calculation without any non-self consistent steps, then I set NELMDL=0. When I do this however, I still get five non-self consistent steps. Is something else over-riding the NELMDL flag (I am using ALGO=NORMAL)?
<span class='smallblacktext'>[ Edited ]</span>