decrease cutoff radius of PAW dataset  [SOLVED]

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dyu
Posts: 5
Joined: Fri Nov 11, 2016 4:18 pm

decrease cutoff radius of PAW dataset

Post by dyu » Mon Nov 14, 2016 11:04 pm

When I run abinit-8.0.8, I got the following error.
-- !ERROR
src_file: chkpawovlp.F90
src_line: 184
mpi_rank: 0
message: |
Action: 1- decrease cutoff radius of PAW dataset
OR 2- ajust "pawovlp" input variable to allow overlap (risky)[/i][/u]

In the middle of output file (see below), it shows the distance between atom 4 (H)and 6 (C) is 2.08 bohr (about 1.1 angstrom).
Therefor the PAW radius of sphere is too large.

My question is the C and H distance is supposed to be around 1.1 angstrom.
Why in PAW data sets (downloaded from website), the PAW radius of sphere is such large that it causes the overlap?
I thought the PAW data sets I downloaded is supposed to be good to apply for many systems.










FFT (fine) grid used in SCF cycle:

getcut: wavevector= 0.0000 0.0000 0.0000 ngfft= 100 100 240
ecut(hartree)= 30.000 => boxcut(ratio)= 2.04449

chkpawovlp : ERROR -
PAW SPHERES ARE OVERLAPPING !
Distance between atoms 4 and 6 is : 2.08018
PAW radius of the sphere around atom 4 is: 0.89889
PAW radius of the sphere around atom 6 is: 1.50737
This leads to a (voluminal) overlap ratio of 5.82 %

COMPENSATION DENSITIES ARE OVERLAPPING !!!!
Distance between atoms 8 and 9 is : 2.39499
Compensation radius around atom 8 is: 1.30053
Compensation radius around atom 9 is: 1.20231
This leads to a (voluminal) overlap ratio of 0.31 %
THIS IS DANGEROUS !, as PAW formalism assume non-overlapping compensation densities.
DATA TYPE INFORMATION:
REAL: Data type name: REAL(DP)
Kind value: 8
Precision: 15
Smallest nonnegligible quantity relative to 1: 0.22204460E-15
Smallest positive number: 0.22250739-307
Largest representable number: 0.17976931+309
INTEGER: Data type name: INTEGER(default)
Kind value: 4
Bit size: 32
Largest representable number: 2147483647
LOGICAL: Data type name: LOGICAL
Kind value: 4
CHARACTER: Data type name: CHARACTER Kind value: 1

ebousquet
Posts: 469
Joined: Tue Apr 19, 2011 11:13 am
Location: University of Liege, Belgium

Re: decrease cutoff radius of PAW dataset  [SOLVED]

Post by ebousquet » Tue Nov 15, 2016 11:33 am

Dear Dyu,
You can increase pawovlp to 10-15%, this is often quite fine too, though always be critic with what you obtain at the end if you go with very large overlaps.
Best wishes,
Eric

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