[CPMD-list] Is it possible to explore chemical reaction using CPMD

[Axel Kohlmeyer]

On Wed, 19 Dec 2007, liu liuxiandong wrote:

XL> Dear CPMDers,

XL>   Is it possible to explore some reactions using CPMD ? For example,

yes. i would say, the main motivation to use DFT instead of a 
force field, is that you can observe chemical reactions.

there are many ways to do this, though, and not all make sense
for all circumstances.

XL> the self-dissociation of water molecule makes material surfaces
XL> hydroxylation. If this can be observed in the simulation, then one 
XL> can
XL> expect a decreasement of the ECLASSIC curve given that the in NVT
XL> ensemble ?  I saw a paper named "J. Phys.: Condens. Matter 17 (2005)
XL> 4005¨C4013 doi:10.1088/0953-8984/17/26/001 Water adsorption on
XL> amorphous silica surfaces: a Car¨CParrinello simulation study". The
XL> authors can observe the decreasement of potential energy curve and
XL> total energy. However, one expect a constant EHAM in a 
XL> well-performed CPMD simulation.

please read the paper you refer to again and have a careful 
look at what kind of MD run was actually done in the CPMD part. 
particularly, what kind of statistical mechanical ensemble 
was the run in, if any?

what are the prerequisites to have a conserved 
quantity, and in particular EHAM?

XL> Any suggestions are appreciated.

if you find a good answer to the two questions above,
you should be able to resolve what is confusing you.

cheers,
    axel.

XL> BEST,

XL> XIANDONGLIU


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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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