[CP2K:4652] The correction of the mean force to calculation of free energy in CP2K

hut... at pci.uzh.ch hut... at pci.uzh.ch
Tue Oct 1 09:16:47 UTC 2013


the answer to all your questions is 'yes'. 

best regards

Juerg Hutter 

Juerg Hutter                         Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich               E-mail:  hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com
From: YE-FEI LI 
Sent by: cp... at googlegroups.com
Date: 10/01/2013 12:20AM
Subject: [CP2K:4652] The correction of the mean force to calculation of free energy in CP2K

Dear CP2K users and developers:
    I am interested into calculation of free energy under a designed reaction pathway, and I have some puzzle about the basic idea for calculating the free energy by utilizing thermodynamic integration and Lagrangian multiplier. The mean force can be obtained from Lagrangian multiplier plus some specific correction according to different constrain. For one bond length constrain, the mean force is the average of Lagrangian multiplier. However, for other constrain, the mean force might not be the average of Lagrangian multiplier, and the correction is needed.
    For instance, if I use the distance difference of r12-r34 as constrain, it seems the mean force is still the average of Lagrangian multiplier. (Am I correct?) However, if I use distance difference of r12-r31 as constrain, it seems the correction is needed, because r12 and r31 is coupled. (Am I correct?) In this case, if I want to calculate the free energy along r12-r31, CP2K will not do the correction automatically, since CP2K only output the Lagrangian multiplier. Thus I must do the correction by myself by using the trajectory of MD? 
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