[Pw_forum] [Fwd: diagonalization failure (david, cg) for large numbers of bands]

[josepht at chips.ncsu.edu]

Hello all,

Thanks Stefano and Brad for responding so quickly!

It indeed runs with a truly massive cutoff (roughly 80 Ry), with regular Davidson
diag (level 4); the 7 needed scf steps took 2:35:24s on 128 processors (Cray XT4). 
The issue is definitely related to needing more PWs, although I do not understand
why such an enormous number is needed.  Indeed, with a reasonable cutoff yielding
several tens of thousands of PWs (more than twice 4*states), seeking to obtain ~3300
KS states did not seem - in my naïveté- to be outrageous.  With the large cutoff
quoted above, 104415 PWs are used.

I will check how much lower the cutoff can be if diagonalizing using Davidson level 2.

Thanks again,

Joseph Turnbull
Department of Physics
North Carolina State University