nagtive value CHGCAR file

Message

hanyuhonest · #1 Post by **hanyuhonest** » Sat Aug 14, 2010 12:19 pm

what does the negative value mean??
my INCAR file:
SYSTEM=ZBNC
ENCUT=500
ISTART=0
ICHARG=2
ISMEAR=0
SIGMA=0.1
#ELECTRONIC PARAMETERS
NELM=300
NELMIN=2
NELMDL=-5
EDIFF=1E-5

ISPIN=2
MAGMOM=22*0 9*0 1 1.5 9*0
ISYM=0

LORBIT=11

LREAL=Auto
LELF=.F.
PREC=A
LVTOT=.T.

IDIPOL=1
DIPOL=0.5 0.5 0.5
LDIPOL=.TRUE.

part of CHGCAR file: (what does the nagtive value mean??)

480 40 216
-.23537897976E-02 -.23364080622E-02 -.23117842029E-02 -.22798764278E-02 -.22411331132E-02
-.21957382518E-02 -.21430913571E-02 -.20818886811E-02 -.20104156752E-02 -.19271920643E-02
-.18321974706E-02 -.17276041581E-02 -.16166552159E-02 -.15015210960E-02 -.13826195586E-02
-.12599910091E-02 -.11344191495E-02 -.10065919672E-02 -.87577383049E-03 -.74013314211E-03
-.59812990711E-03 -.44886408052E-03 -.29134016106E-03 -.12446219180E-03 0.51919063414E-04
0.23658745250E-03 0.42774463509E-03 0.62346377228E-03 0.82118186618E-03 0.10179203836E-02
0.12120073800E-02 0.14038651707E-02 0.15937897997E-02 0.17792340483E-02 0.19558940311E-02
0.21220458301E-02 0.22805879160E-02 0.24358298319E-02 0.25890720906E-02 0.27385436668E-02
0.28832358004E-02 0.30252639816E-02 0.31680880806E-02 0.33135826569E-02 0.34615716800E-02
0.36112302465E-02 0.37614463837E-02 0.39095341195E-02 0.40503853449E-02 0.41775338112E-02
0.42853955175E-02 0.43712782089E-02 0.44364285879E-02 0.44856765928E-02 0.45254139321E-02
0.45607718054E-02 0.45938847194E-02 0.46242471071E-02 0.46502140296E-02 0.46702028188E-02
0.46833854411E-02 0.46903256134E-02 0.46931751040E-02 0.46946103595E-02 0.46960017323E-02
0.46966331292E-02 0.46949598961E-02 0.46907461619E-02 0.46861089227E-02 0.46847414340E-02
<span class='smallblacktext'>[ Edited ]</span>

metosa · #2 Post by **metosa** » Sat Aug 14, 2010 9:15 pm

Since your calculation is spin polarized, CHGCAR contains two data grid. First one is "spin_up plus spin_down" grid and the second one is "spin_up minus spin_down" grid. It is normal that second grid can have negative values.

hanyuhonest · #3 Post by **hanyuhonest** » Sun Aug 15, 2010 1:40 am

Thank you metosa!
But the negative values are also appear in the first contains and some other non-spin polarized calculations?

forsdan · #4 Post by **forsdan** » Sun Aug 15, 2010 7:14 am

Small negative values in the charge density can arise e.g. if you have a vacuum region. Please see the comments in the FAQ:

http://cms.mpi.univie.ac.at/vasp/vasp/FAQ.html

Cheers,
/Dan

hanyuhonest · #5 Post by **hanyuhonest** » Sun Aug 15, 2010 3:49 pm

Dear fosdan~~
Should I need to avoid these negative values??