[QE-users] Blue moon ensemble calculations in quantum espresso

[Giovanni La Penna]

Payal,

It is possible to use QE with PLUMED and then to apply PLUMED recipes:

https://www.plumed.org

Recently blue-moon sampling has been done with PLUMED combined together
with other DFT codes:

https://doi.org/10.1007/s11244-021-01516-y

The last time I used PLUMED 1.x in QE 5.2 (2016) to perform manipulations
(not properly a correct sampling):

https://doi.org/10.3390/molecules23123308

With a little handcraft, it is possible to use PW of QE 7.0 with PLUMED 2.7.x.
Unfortunately not yet CP, as far as I know.

HTH,
          Giovanni

On Mon, Dec 12, 2022 at 09:59:48PM +0000, Payal Chaudhary wrote:
> I had a question about running blue moon calculations with Quantum Espresso.
> 
> To get the free energy profile along a reaction coordinate, we can run several constrained MD calculations and use the blue moon ensemble averages to get free energy gradients. These gradients can then be integrated to get the free energy profile. This methodology is described in the paper "Giovanni Ciccotti & Mauro Ferrario (2004) Blue Moon Approach to Rare Events, Molecular Simulation, 30:11-12, 787-793" (doi<https://doi.org/10.1080/0892702042000270214>)
> 
> To calculate these averages, we need some quantities in the output file, such as the metric tensor z, and the Lagrange multiplier λ, for each time step. In the case of VASP, these can be obtained by specifying an additional input tag.
> 
> The QE docs are not clear on whether these quantities are printed in the output, and I couldn't find any discussion on this in the forums either.
> I would really appreciate if someone could point me in the right direction to compute blue moon ensemble averages with the QE code.
>