[QE-users] Binding energy and interatomic force constant

[KRISHNENDU MUKHERJEE]

Dear all, 

Thank you for continuing the discussion. Please allow me to write why I asked the question. I am trying to find out a methodology to find the effect of grain-size on binding energy. I think one way is to compare the total-energy of the system from pwscf calculation for different grain-sizes. But then I think the total-energy will also include the surface energy. So, now I put my question in a different way. Is there a way to find out the binding energy from the total-energy ? 

Thank you, 
Regards, 
Krishnendu 

------------------------------------------------------------------------------------------------------------------ 

Dear Prof. Baroni, 

Hi. 
Thank you so much for your detailed clarification. 

Best regards, 
Mahmoud Payami 
----- Original Message ----- 
From: Stefano Baroni (BARONI at sissa.it) 
Date: 07/01/1403 21:53 
To: Mpayami (mpayami at aeoi.org.ir), Quantum ESPRESSO users Forum (users at lists.quantum-espresso.org) 
Subject: Re: [QE-users] Binding energy and interatomic force constant 

Here, I beg to differ. The binding is defined as the energy necessary to bring all the atoms from their equilibrium position (Δx=0) to an infinite distance from each other (Δx=\infty). In any harmonic model, evidently, this energy would be infinite. The problem is, the harmonic model, within which interatomic force constants are defined, is only meaningful in the neighbourhood of the equilibrium position and does not say anything about the forces acting on atoms far from it. Hope this clarifies a bit. Stefano B 


On 26 Mar 2024, at 18:51, Mpayami via users <users at lists.quantum-espresso.org> wrote: 


Dear Krishnendu, 

Hi. 
I add a few words to Prof. Stefano Baroni's reply: 
Suppose you have a harmonic spring obeying Hook's law, for which the stored energy is E=K*(Δx)^2/2. 
Here, K plays the role of interatomic force constant. As you see, just knowing K one can not calculate 
the stored energy unless on knows the value of Δx. 

Bests 

------------------------------- 
Mahmoud Payami 
NSTRI, AEOI,Tehran, Iran 
Email: mpayami at aeoi.org.ir 
Phone: +98(0)2182066504 
------------------------------------ 

----- Original Message ----- 
From: Stefano Baroni (baroni at sissa.it) 
Date: 06/01/1403 11:41 
To: Quantum ESPRESSO users Forum (users at lists.quantum-espresso.org) 
Subject: Re: [QE-users] Binding energy and interatomic force constant 

No. SB 

___ 
Stefano Baroni, Trieste --http://stefano.baroni.me 

On 25 Mar 2024, at 07:15, KRISHNENDU MUKHERJEE <krishnendu at nmlindia.org> wrote: 




Dear all, 


Can I compute the binding energy of a nano-crystal from the interatomic force constant ? 


Thanking you, 
Best regards, 
Krishnendu 




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20240327/d3ce15bd/attachment.html>