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[vincent.chevrier@dahn.phys.dal.ca]

Hi,
I've recently begun using Abinit and have gone through the basic tutorials. 
I'm trying to run an energy calculation of Li15Si4. The primitive cell is 
sizeable (30 Li, 8 Si) and I'm having difficulty establishing the appropriate 
ecut and ngkpt (or nkpt).

Here's a table of energies (in Ha). If anyone could tell me why the energy 
starts varying so wildly as the k points are increased or if anyone has any 
recommendations as to which parameters I should use I would really appreciate 
it! 

ecut\ngkpt (nkpt)

        2 2 2 (2)       4 4 4 (6)      10 10 10 (44)   12 12 12 (68)
30      -42.500550      -42.500085      -56.940709      -43.130515
35      -42.500777      -42.500314      -61.734328      -42.554030
40      -42.500897      -42.500449      -86.955397      -149.902062
45      -42.500918      -42.500504      -42.604657      -260.973168
50      -42.500920      -42.500457      -42.566132      -158.776883
55      -42.500928      -42.500670      -44.279878      -48.285954
60      -42.500936      -42.500489      -75.221022      -43.411153

The .in, .out and log files, of the ngkpt 12 12 12 case are at the following 
address (if you're really interested!). The other energies were generated 
with the exact same input files with only the ngkpt changed.
http://myweb.dal.ca/chevrier/abinit/ecut_LDA_22.in
http://myweb.dal.ca/chevrier/abinit/ecut_LDA_22.out
http://myweb.dal.ca/chevrier/abinit/log_Li15Si4_ecut_LDA_22

I'm running this with the parallel version.
Thanks!

Vincent Chevrier
PhD Candidate
Physics Department
Dalhousie University