[gpaw-users] Van der Waals correction

[Rico Friedrich]

Dear GPAW users,

I try to do a calculation with a molecule adsorbed on an Au-surface  
and want to use the Van der Waals correction of Tkatchenko and  
Scheffler for geometry optimization. Calculations on the pure  
molecular structure without the gold atoms work fine. Then I obtained  
the values for the C6 coefficient and the other parameters in the  
vdwcorrection.py file for gold Ruiz et al. PRL 108 (2012). However  
when I include the gold atoms in the relaxation I still get an  
error-message including the following lines:

cc = vdWTkatchenko09prl(HirshfeldPartitioning(c),  
vdWradii(aupc.get_chemical_symbols(), 'PBE'))
   File "/home/friedrir/lib/python/gpaw/analyse/vdwradii.py", line 54,  
in vdWradii
     cc = vdWTkatchenko09prl(HirshfeldPartitioning(c),  
vdWradii(aupc.get_chemical_symbols(), 'PBE'))
   File "/home/friedrir/lib/python/gpaw/analyse/vdwradii.py", line 54,  
in vdWradii
     n_g, r_g = get_density(Zrg)
   File "/home/friedrir/lib/python/gpaw/analyse/vdwradii.py", line 35,  
in get_density
     n_g, r_g = get_density(Zrg)
   File "/home/friedrir/lib/python/gpaw/analyse/vdwradii.py", line 35,  
in get_density
     xc, world)
   File "/home/friedrir/lib/python/gpaw/setup.py", line 1018, in __init__
     xc, world)
   File "/home/friedrir/lib/python/gpaw/setup.py", line 1018, in __init__
     symbols = [chemical_symbols[Z] for Z in Z_a]
TypeError: list indices must be integers, not NoneType
GPAW CLEANUP (node 3): <type 'exceptions.TypeError'> occurred.   
Calling MPI_Abort!
     symbols = [chemical_symbols[Z] for Z in Z_a]


Is there any idea how to overcome the problem. Thanks in advance.

Best regards,

Rico Friedrich