can cpmd run for chemical reaction?

The answer is yes. The following information is from CPMD list by Prof. Hutter.

Hi

> Dear Prof. Hutter:
>     We are currently testing chemical reaction by CPMD.  I have some
> puzzles with the following questions:
>
> 1. How to construct pseudopotentials and pseudowavefunction for cation
> and anion?
>     We have tested to use neutral atomic pseudopotential, for example
> Cl, and use the "ATOMIC CHARGE" with value -1.0 to run Cl- anion.
> However we always get the same neutral result.  Should we use anion Cl-
> pseudopotentials?

The basic idea is to have one PP for all possible states of an atom
(transferablility) including anion and cations. Of course
you can also construct PP using an ion as reference state.

In a ab initio program you only specify the total number of
electrons of the whole system. Default is to use the number of electrons
to achieve charge neutrality. This can be changed using the CHARGE
keyword.
ATOMIC CHARGE is only used for the initial guess and can usually
be ignored.

>
> 2. In your paper, Chem Phys. Lett., 321(2000)225, about proton transfer
> how to generate H+ cation pseudopotential?

Use the normal H PP (see above)


> According to Fig. 2 in that paper, it seems to me all of the atoms of
> (H2O)3H+ move.  Does H+ transfer to water 3??
>
There is no distiction of H and H+. We see proton transfer several times.

> 3. If the answer for question 1 is that we have to use negative charged
> pseudopotentials, then this question is puzzle to us.
> We want to study Cl- anion(incoming) + ClCCH2CN, S_N2 reaction, the
> incoming Cl- has to  use negative charged pseudopotentials and the
> outgoing Cl at beginning has to use neutral pseudopotentials.  After the
> reaction the incoming particle has to use neutral pseudopotential and
> the outgoing Cl has to use negative charged pseudopotentials.  This
> question is similar to question 2.
>
see above


> If the answer for the anion and cation pseudopotentials should all use
> neutral pseudopotentials, then how to make "ATOMIC CHARGE" works?
>
see above

> 4. We want to study another S_N2 reaction of O(1D) +CH4, where 1D is the
> term symbol.  The oxygen is in its excited state.  Can we use tddft to
> excite oxygen atom to its excited state and then write out its
> wavefunction with fixed term symbol.  How and which files story this
> information?
> Then the next question is to read in the restart file for oxygen only
> and put CH4 as initial run.  Can this work? and how?
>
This is not possible.

regards

Juerg Hutter