[CPMD-list] Davidson diago of TDDFT

[Juerg Hutter]

Hi

> Dear List Subscriber,
>
> I am trying to calculate electronic spectra using TDDFT (v3.9.1).  When some of
> the roots are not converged after the Davidson diago step of the TDDFT matrix, I
> understand RDIIS kicks in.  What puzzles me in my calculation is the point where
> this transition takes place.  It seems to me that RDIIS is switched on even
> though either MAX ITER or MAX SUBSPACE of DAVIDSON DIAGO has not been exceeded
> (see portions of my output below).  Is there a third criterion to stop DAVIDSON?
>  Thanks very much for reading.

If progress in the Davidson diagonalisation is very slow and the gradient
is small enough, the program switches to RDIIS. This can be controled by

  DAVIDSON RDIIS
   nrdiismax,nrestdmax,rdiistin

where nrdiismax is max number of rdiis steps
nrestdmax maximum number of restarts
rdiistin minimum gradient to start RDIIS

regards

Juerg Hutter




>
> Best regards,
>
> EG Kim
>
> #############################################################################
>
>  *********************** LINEAR RESPONSE ************************
>  Step size for numeric dmu/dn :                          .500E-02
>  Number of calculations for dmu/dn :                            2
>  Maximum number of optimisation steps:                       1000
>  Threshold for Hessian (Preconditioner)                     .5000
>  Optimizer for LR equations                             AUTOMATIC
>                     Size of ODIIS buffer                        5
>                     Size of ZDIIS buffer                        4
>                     Switch from PCG to ODIIS at         .1000E+00
>                     Switch to full preconditioning at   .1000E-02
>  Step length                                                .1000
>  Convergence criteria                                   .1000E-04
>  ****************************************************************
>
>  ***************************  TDDFT  ****************************
>  Step size for numeric dmu/dn :                          .500E-02
>  Number of calculations for dmu/dn :                            2
>  Tamm-Dancoff Approximation
>  Diagonalization Method                                  DAVIDSON
>           Max. number of iterations                           200
>           Convergence criteria                           .100E-06
>           Max. size of Davidson matrix                         50
>           RDIIS Parameters
>           NTDIISMAX=  20      NRESTDMAX=   3  RDIISTIN=  .100E-02
>  Number of Singlet States                                       3
>  Forces calculated for state                                    1
>  ****************************************************************
> .
> .
> .
> .
> .
> ***   SPECTRA| THE NEW SIZE OF THE PROGRAM IS 286956 KBytes ***
>  ==                      SINGLET STATES                        ==
>  NUMBER OF STATES TO BE INITIALIZED                             3
>  TOTAL NUMBER OF TEST VECTORS                                   6
>  ***   SPECTRA| THE NEW SIZE OF THE PROGRAM IS 319776 KBytes ***
>  ================================================================
>  ==            DAVIDSON DIAGONALISATION OF TDDFT MATRIX        ==
>  ================================================================
>   ITER      STATES      SUBSPACE             RESIDUAL        TCPU
>      1           0             3        .13533773E-01       87.40
>      2           0             6        .46776986E-02       88.93
>      3           0             9        .30463019E-02       90.23
>      4           0            12        .33203299E-02       91.35
>      5           0            15        .22075106E-02       93.19
>      6           0            18        .11336981E-02       96.40
>      7           0            21        .67511167E-03       98.32
>      8           0            24        .64601509E-03      100.01
>      9           0            27        .57523001E-03      105.70
>     10           0            30        .47208419E-03      373.56
>     11           0            33        .36949736E-03      253.12
>     12           0            36        .40133983E-03      752.00
>     13           0            39        .59391461E-03     2563.71
>  >>> RESIDUAL DIIS OPTIMIZATION OF ROOT                         1
>   ITER      ENERGY      SUBSPACE             RESIDUAL        TCPU
>      1     2.88328             1        .30627204E-04      108.58
>      2     2.88311             2        .82109007E-05      155.98
>      3     2.88299             3        .66425066E-05       61.41
>      4     2.88291             4        .43031780E-05       53.93
> .
> .
> .
> .
> .
>
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