WIEN2k-FAQ: How to select the first radial mesh point R0 (overcomming the "R0 for atom too big" warning)?

©2001 by P. Blaha, K. Schwarz and J. Luitz

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Problem: lstart gives a warning "R0 for atom too big"

The parameter R0 in case.struct gives the distance between the nucleus and the first point in a radial mesh. If this first point is too far away from the nucleus, then the steep variations of the orbitals close to the nucleus are not properly described. A warning will be given by lstart in such cases :

WARNING: R0 for atom 1 Z= xx.xx too big

Proper values for R0 depend on the Z-value of the atom only. They are set automatically if you use w2web, makestruct or cif2struct to generate your structure. If you create your case.struct manually (especially when recycling a case.struct from a previous calculation), these are the values to take (see $WIENROOT/SRC_structeditor/bin/getar0.m) :
H to Ar:   R0 = 0.000100
K to Kr:   R0 = 0.000050
Rb to Lu : R0 = 0.000010
Hf to ...: R0 = 0.000005

Peter Blaha,