[CPMD-list] PBE + NLCC convergence problem

[Axel Kohlmeyer]

>>> "OY" == Oleg Yazyev <oleg.yazyev at epfl.ch> writes:

OY> Dear cpmd community,

OY> I've found the strange problem. Probably, somebody already have seen
OY> this and know how to solve it or this observation will help to fix
OY> some bugs.
OY> Generally, when using PBE GGA and pseudopotentials with NLCC SCF
OY> always blows up after few first iterations (see below the example).

hi,
could you please post some more information about the 
pseudopotentials, you are using. 

OY> The problem is well reproducible (at least all openshell molecular
OY> systems I'm interested in shows this behaviour) but appears only with
OY> PBE GGA (at least LDA, BP and BLYP are OK) and never appears if NLCC
OY> is not used.

i'm not so sure, if this applies here, but i have seen, that the
line search occasionally gets diverted for some systems in the initial
state of the optimization (too much noise). in those cases, i could get 
to convergence, by first using ODIIS until it was 'stuck' and then 
continue with PCG MINIMIZE. you should check, however, if the results
are physically reasonable.

also, did you check, how much this is affected by GC-CUTOFF?

and finally, does the same setup work in closed shell cases?

regards,
        axel.

OY>  NFI      GEMAX       CNORM           ETOT        DETOT      TCPU
OY>    1  1.994E-02   2.166E-03      -7.223573    0.000E+00     44.19
OY>  LINE SEARCH : LAMBDA=.422     PREDICTED ENERGY = -7.361147976013
OY>    2  1.624E-02   1.836E-03      -7.281170   -5.760E-02     44.01
OY>  LINE SEARCH : LAMBDA=.633     PREDICTED ENERGY = -7.407550491052
OY>    3  9.908E-03   1.222E-03      -7.361091   -7.992E-02     43.86
OY>  LINE SEARCH : LAMBDA=.158     PREDICTED ENERGY =  8.255565606249
OY>    4  1.716E+02   2.868E+01      -7.407496   -4.641E-02     42.93
OY>  LINE SEARCH : LAMBDA=.475     PREDICTED ENERGY =  6.515199589623
OY>    5  5.391E+01   1.544E+01       6.515225    1.392E+01     42.56
OY>  LINE SEARCH : LAMBDA=.712     PREDICTED ENERGY =  6.515174606737
OY>    6  6.666E+01   2.017E+01       6.515202   -2.253E-05     42.59
OY>  LINE SEARCH : LAMBDA=1.07     PREDICTED ENERGY =  6.514689978070
OY>    7  1.564E+01   5.375E+00       6.515178   -2.471E-05     42.64
OY>  LINE SEARCH : LAMBDA=1.60     PREDICTED ENERGY =  6.514698812780
OY>    8  3.005E+01   2.038E+01       6.514744   -4.335E-04     42.87
OY>  LINE SEARCH : LAMBDA=2.40     PREDICTED ENERGY =  6.513880859113
OY>    9  9.822E+00   4.859E+00       6.514704   -4.031E-05     42.47
OY>  LINE SEARCH : LAMBDA=3.60     PREDICTED ENERGY =  6.513401997207
OY>   10  2.021E+01   6.364E+00       6.513972   -7.315E-04     42.84


OY> -- 
OY> Best regards,
OY>  Oleg


OY> ______________________________________________________
OY> Oleg Yazyev
OY> Institute of Molecular and Biological Chemistry
OY> Swiss Federal Institute of Technology in Lausanne (EPFL)
OY> EPFL - BCH
OY> CH-1015 Lausanne (Switzerland)
OY> Tel.: +41 21 693 9881
OY> E-mail: oleg.yazyev at epfl.ch
OY> WWW: http://icmbcu001.epfl.ch/yazyev/index.html
OY> _______________________________________________________

OY> _______________________________________________
OY> CPMD-list mailing list
OY> CPMD-list at cpmd.org
OY> http://cpmd.org/mailman/listinfo/cpmd-list



--

=======================================================================
Axel Kohlmeyer       e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.