why energies the same?

[Chetan Mahajan]

Hi Folks

I am new to this field, learning it. We are carrying out AIMD simulations using cp2k of water solvated acidic-basic membrane systems. I have a question as follows:

For three different configurations of atomic nuclei, initial potential energy as calculated by cp2k is almost same around -3128 Hartree. 

These configurations are 

1. Configuration at the end of classically equilibrating the system with DREIDING hydrogen bonding potential ON

2. Configuration at the end of classically equilibrating the system with such potential OFF

3. Initial configuration BEFORE any classical equilibration. 

Isn't the potential energy supposed to vary with change in nuclear positions? 

If case 1 and 2 are same, fine a possibility, but even case 3 is same, which is very strange. It's a system completely away from classical equilibrium. 

Thanks

Chetan

--
Chetan V Mahajan
PhD candidate, Ganesan Group
Department of Chemical Engineering
The University of Texas at Austin

[Teodoro Laino]

Hi Cheta,

"around -3128 Hartree [..]" means almost nothing. Keep in mind that 1 H is a huge quantity, so differences of 0.1 are still pretty significant.
Of course there is always the (remote) possibility that you have some errors in your input files. Unfortunately, that's only speculation, unless you do not share them with all the Folks here...

Cheers
Teo

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[Chetan Mahajan]

Hi Teo

Yeah, you are right! My lowest difference is 0.162 H and it is significant when I convert to kcal/mol. I was just not sure how to rate the significance of these numbers when nuclear configurations are changing quite a bit. Now I know even these differences matter. 

Thanks

Chetan