Different grid points about CHGCAR

[Yongju]

Hello, I need some help about CHGCAR file.
I want to visualize charge difference with VESTA program about Ni/WC system. But among CHGCAR files (Ni/WC, Ni, WC), only Ni CHGCAR file has different grid points. Ni/WC and WC have 56*56*280 but Ni has 54*54*250. Lattice vectors in POSCAR, KPOINTS, INCAR is all same. Of course atomic coordination in POSCAR is also fixed. I don't know why those grid points are different. The following information is my INCAR and POSCAR files of Ni/WC, Ni and WC.

Ni/WC INCAR

SYSTEM = NiWC
Starting parameters for this run:
NWRITE = 2 write-flag
ISTART = 0 job : 0-new, 1-cont, 2-samecut
ICHARG = 2 charge: 0-wave, 1-file, 2-atom, >10-const
INIWAV = 1 electr: 0-lowe 1-rand 2-diag

Electronic Relaxation:
PREC = high low | medium | high
ENCUT = 500 kinetic energy cutoff (eV)
ISPIN = 2

NELMDL = -11 number of delayed ELM steps
NELM = 1000 number of ELM steps
EDIFF = 1E-05 energy stopping-criterion for ELM
LREAL = AUTO real-space projection (.FALSE., .TRUE., On, Auto)
IALGO = 48 algorithm (8=CG for small, 48=RMM for big systems)
ADDGRID = .TRUE.


LWAVE = .TRUE.
#LPARD=.TRUE.
LCHARG=.TRUE.
#EINT=-0.9790 -0.9590
NBMOD=-3

##LDA+U
LDAU = .TRUE.
LDAUTYPE = 2
LDAUL = -1 -1 2 = -1 -1 (WC INCAR) = 2 (Ni INCAR)
LDAUU = 0 0 8 = 0 0 (WC INCAR) = 8 (Ni INCAR)
LDAUJ = 0 0 0.95 = 0 0 (WC INCAR) = 0.95 (Ni INCAR)
LDAUPRINT = 2 = 2 (WC INCAR) = 2 (Ni INCAR)

LPSORBIT = .TRUE.
LASPH = .TRUE.

LORBIT = 11

## Van der Waals
LVDW = .FALSE.
# LDW_RADIUS = 30.0
# VDW_SCALING = 0.75
# VDW_D = 20.0
# VDW_C6 = 24.67 12.64 0.000 1.23 1.75 0.14 0.70
# VDW_R0 = 1.606 1.771 1.000 1.397 1.452 1.001 1.342

NSW = 2000 max number of geometry steps
# NELMIN = 6
IBRION = 2 ionic relax: 0-MD, 1-quasi-Newton, 2-CG, 3-Damped MD
EDIFFG = -0.01 force (eV/A) stopping-criterion for geometry steps
ISIF = 1 (1:force=y stress=trace only ions=y shape=n volume=n)
ISYM = 1 (1-use symmetry, 0-no symmetry)
POTIM = 0.3 initial time step for geo-opt (increase for soft sys)

# DOS related values:
ISMEAR = -1 (-5:tet_b,-4:tet,-3:scan,-1:Fermi,0:gaus,1:MP)
SIGMA = 0.02 broadening in eV
#
NPAR= 4
LPLANE = .TRUE.
RWIGS = 1.455 0.863 1.286 = 1.455 0.863 (WC INCAR) = 1.286 (Ni INCAR)


Ni/WC POSCAR

Ni
1.00000000000000
5.0330000000000004 0.0000000000000000 0.0000000000000000
-2.5165000000000002 4.3587058572000004 0.0000000000000000
0.0000000000000000 0.0000000000000000 24.7252902940000006
W C Ni
15 12 20
Direct
0.9854402114756113 0.9830371587483602 0.9982635150633217 F F F (repeat)
0.6563929605965040 0.3272730832812467 0.0000318272136225
0.3229683732444586 0.6588612879324613 0.0000866905641145
0.9872784972058686 0.9882699699492037 0.1138306415035762
0.6538978291317123 0.3214603868457107 0.1139337600492322
0.3201574393958360 0.6545958775667660 0.1139730492847234
0.9859055523045293 0.9868323810473527 0.2296133474667093
0.6523590909127754 0.3201323780766868 0.2297144908696166
0.3192037503476397 0.6533149025909573 0.2296698660422863
0.9847924778647091 0.9859570179335272 0.3453274765600032
0.6513981900407445 0.3190915360437666 0.3455019748642962
0.3179253380045535 0.6522435791846654 0.3453079779666148
0.9850053050362338 0.9851860817039245 0.4592133268957355
0.6471663131822417 0.3154637486784994 0.4613156038252080
0.3197659747274908 0.6542021103403233 0.4589443726658450
0.3209931872947858 0.9901957967395614 0.0555406958647438
0.9882353233555291 0.3200174013419463 0.0551729889938817
0.6548696907524622 0.6565780463532254 0.0558066406418078
0.3198861136291984 0.9876298809740602 0.1716433163077760
0.9864482914798088 0.3206045454747899 0.1716090156543025
0.6531387473356897 0.6542079763282523 0.1716533961123214
0.3185455721296556 0.9863169455228966 0.2876265211524995
0.9850947334911566 0.3195853297133171 0.2876614621128739
0.6520330396443198 0.6530278546576332 0.2876267297437458
0.3183360571365242 0.9862246547687584 0.4035895593483624
0.9820414922925501 0.3186515335088384 0.4040136938188459
0.6513507257246097 0.6501480704932080 0.4037623200899164 - WC POSCAR
0.0151061619120581 0.0538597287297860 0.8975389946050185
0.4891855082737238 0.0231304115076354 0.9072044442584473
0.0021312471781681 0.5222441649680807 0.9069141003686525
0.5234302324356022 0.5426064205761344 0.9075902215726691
0.6895213742235086 0.3511876519296359 0.8181463432318541
0.1911840817192454 0.3566250351849641 0.8150233371788281
0.6864968247488082 0.8512375501767855 0.8175886111507842
0.1840942826459089 0.8533262205925750 0.8176683001773957
0.3541961449694991 0.6648382394704523 0.7289917298375452
0.8580308194772406 0.6665452028923433 0.7295527076883859
0.3549799207504872 0.1671960770665215 0.7297131144266882
0.8489493720563688 0.1582117445869928 0.7290850535400455
0.0102369757669158 -0.0051003004136945 0.6393449243548180
0.5106111106884073 -0.0030346905940754 0.6406404616838508
0.0140765855168273 0.4974475094533928 0.6423010599086250
0.5124565832666607 0.4951513708097858 0.6431136317018772
0.6973788762344547 0.3672737068183600 0.5616377735064881
0.1602599227238088 0.3387902438144933 0.5515883409091397
0.6698119423590525 0.8315638431872218 0.5516755145694441
0.1995716843248428 0.8700827485831317 0.5498781337441597 - Ni POSCAR

[graeme]

You can use the NGXF, NGYF, and NGZF tags to manually set the FFT grid.

[Yongju]

Thank you for your reply.

As you mentioned, I knew FFT grid can be determined by NGXF etc.. but I don't know where and how should I write those NGXF, NGYF, NGZF in INCAR file. If I want 56*56*280 grid, should I write NGXF=56, NGYF=56, NGZF=280?