[CPMD-list] I cant use ODIIS NO_RESET

[Salomon Billeter]

Hi Cao Dayong,

> &CPMD
>   ODIIS  NO_RESET
>   OPTIMIZE GEOMETRY XYZ
>   ISOLATED MOLECULE
> &END

both ODIIS and NO_RESET need a value. At the moment, NO_RESET is
implemented as a keyword on its own, i.e. it must not appear on the same
line as e.g. ODIIS. An example is here:

&CPMD
  ODIIS
    5
  NO_RESET
    20
  OPTIMIZE GEOMETRY XYZ
  ISOLATED MOLECULE
&END

This means that you use 5 steps for DIIS and reset DIIS after 20 steps if
the progress is not good enough (or -1 if you want to switch off resetting
DIIS altogether).

For a geometry optimization, you can also try adapting the tolerance of the
wavefunction to the nuclear gradient. You are going to save wavefunction
cycles, and maybe don't even need NO_RESET. Here is an example:

&CPMD
  ...
  CONVERGENCE ADAPT
    0.02
  CONVERGENCE RELAX
    25
&END

In addition, the lines CONVERGENCE RELAX and 25 make the wavefunction
convergence criteria temporarily relax by a factor of two every 20
wavefunction cycles until the next geometry step which resets them. For
details of adaptive tolerance, see the manual.

Best regards,
Salomon