ROPT
ROPT = [real array], one entry for each species on the POTCAR file
| Default: ROPT | = 0.67 | if LREAL=On and PREC=Low |
| = 1.0 | if LREAL=On and PREC=Med | |
| = 1.5 | if LREAL=On and PREC=High | |
| = 0.01 | if LREAL=Auto and PREC=Low | |
| = 0.002 | if LREAL=Auto and PREC=Med | |
| = 1E-4 | if LREAL=Auto and PREC=High |
Description: ROPT determines how precise the projectors are represented in real space.
Optimization of the real space projectors maximal supplied Q-value = 12.85 optimization between [QCUT,QGAM] = [ 4.75, 9.51] = [ 6.33, 25.32] Ry Optimized for a Real-space Cutoff 2.30 Angstroem l X(QCUT) X(cont) X(QGAM) max X(q) W(q)/X(q) e(spline) 0 9.518 9.484 -.004 18.582 .11E-03 .16E-06 0 -2.149 -2.145 .001 3.059 .17E-03 .25E-06 1 8.957 8.942 .003 9.950 .14E-03 .34E-06 1 1.870 1.870 .001 1.837 .95E-03 .51E-06 2 3.874 3.866 .000 4.764 .15E-03 .68E-07
QCUT and QGAM are parameters chosen for the generation of this particular PAW dataset (or ultrasoft pseudopotential). The most important information is given in the column W(q)/X(q) (respectively the column W(low)/X(q) for LREAL=Auto). The values in these columns must be as small as possible. If these values are too large, increase the ROPT from the default value. As a rule of thumb the maximum allowed value in this column is 10-3 for PREC=Med. (For PREC=Low errors might be around 10-2 and for PREC=High errors should be smaller than 10-4). If W(q)/X(q) is larger than 10-2 the errors introduced by the real space projections can be substantial. In this case ROPT must be specified in the INCAR file to avoid incorrect results. If the new "precision" mode is used in VASP.4.4 (ROPT<0.1) the code automatically selects the real-space cutoff so that the required precision is reached.