Question about Negative Chemical shift value

[dbkyj]

I'm trying to calculate NMR chemical shift for Hydrogen molecule with vasp 5.3.5.

In literature, H chemical shift is always positive,
but vasp gives negative chemical shifts of H atoms.

For H2, LiH, CH4 molecule, vasp's chemical shift are -26.1, -27.08, -31.0 ppm(negative). while in PRL, 77, 5300, these value is 25.9, 26.6, 30.7 ppm (positive).

If chemical shift is negative in vasp OUTCAR,
should we get only absolute value ?

Is there any problem in my input ?



INCAR
ENCUT = 600.000
PREC = A
EDIFF = 1e-12
LCHIMAG = .TRUE.
ISMEAR = 0
SIGMA= 0.1
DQ = 0.001
ICHIBARE = 1
LNMR_SYM_RED = .TRUE.
NSLPLINE = .TRUE.

POSCA
H2
1.00000000000000
20.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 20.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 20.0000000000000000
H
2
Direct
0.0000000000000000 -0.0002705143867102 0.0000000000000000
0.0000000000000000 0.0372705143867092 0.0000000000000000

0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00

[admin]

VASP actually calculates a chemical shielding, not a shift.
you have to multiply your shifts with -1 if you want to compare vasp-results with this paper of Mauri et al.