Questions tagged [free-energy]

Questions about free energy.

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Relationship between grand potential and free energy?

What is the fundamental relationship between grand potential and free energy? In other words, what assumptions need to be made in order to obtain the free energy equation rather than the grand ...
7 votes
1 answer
93 views

Water Dimer and Free Energy Perturbation (FEP)

I am trying to understand the FEP in the context of water dimer. Let's say I want to calculate $\Delta A$, the free energy change for the following reaction: $\ce{H_2O +H_2O\rightarrow H_2O-H_2O}$, ...
6 votes
0 answers
90 views

Calculating enthalpy of a chemical reaction using DFT

Let's say we have a decomposition reaction $A \rightarrow B + C$ how would I go about calcualting the Enthalpy of this chemical reaction using VASP. I am gonna describe what I am thinking below please ...
6 votes
0 answers
170 views

How to calculate the Gibbs free energy for a reaction?

I am trying to learn how to calculate Gibbs free energy for a reaction. Assuming a reaction for two-dimensional TMDCs: MoS2 (solid) + 2Se(gas) ---> MoSe2 (solid)+ 2S (gas) I can calculate the ...
5 votes
1 answer
139 views

How to estimate chemical potential at a temperature?

Fermi level is electron chemical potential at 0K and we can obtain it from DFT calculation. However, the chemical potential is dependent on temperature. But I only find the equation for gas or simple ...
  • 1,813
5 votes
3 answers
148 views

Gibbs free energy modification after finishing NEB?

I have finished the NEB calculation, but it seems all the energy I got is Internal energy instead of Gibbs free energy, so do I need to do Gibbs free energy modification? Is there any standard ...
  • 1,843
3 votes
0 answers
203 views

What input setting in Quantum ESPRESSO will allow me to calculate the free energy of a solid? [closed]

I understand that it's possible to calculate the Gibbs free energy of a system ab initio, see for example: How can we calculate the Gibbs free energy from first principles? I'm wondering how I can do ...
  • 3,609
10 votes
1 answer
136 views

Should one consider the spatial degeneracies of the electronic state while calculating the Gibbs free energy?

The Gibbs free energy of a molecule is generally expressed as a sum of translational, rotational, vibrational, electronic and nuclear contributions. The electronic contribution $G_{elec}$ is formally ...
  • 7,498
5 votes
1 answer
112 views

Software for generating ensembles of dimer pairs of organic molecules

For two organic molecules of essentially unlimited size (up to and including, and sometimes exceeding MW = 1000 g/mol), I would like to generate all possible dimer pairs in vacuum. The pairs may be ...
  • 1,030
10 votes
0 answers
97 views

Single electron transfer periodic DFT in VASP [closed]

I have the following question: I am currently studying the electrocatalytic $\ce{CO2}$ reduction reaction (CO2RR) on $\ce{Cu}$ materials using periodic DFT calculations and I am using the ...
10 votes
1 answer
197 views

Can I compute the free energy difference in (temporally) nearby micro-states using the Zwanzig equation for Free Energy Perturbation?

I wanted to understand the Free Energy Perturbation in an NVT ensemble. Wikipedia explains it as: $$ \tag{1} \Delta F = F_1 - F_0 = -\kappa T \ln \left<\exp\left( \frac{-(E_1-E_0)}{\kappa T}\right)...
  • 1,083
11 votes
0 answers
160 views

Calculate free energy for a canonical (NVT) ensemble [closed]

Note: Users wishing to answer this question may write a comment or a message in the chat indicating their desire for the question to be re-opened. I have an NVT ensemble of water molecules (liquid) ...
  • 1,083
19 votes
1 answer
819 views

Difference between potential energy, free energy and Coulomb energy in solid state physics

I often encounter terms such as (Helmholtz, Gibbs) free energy, potential energy and total energy when describing the energy of a physical system at atomic level. Sometimes I stumble upon Coulomb ...
12 votes
3 answers
352 views

Is there any definitive evidence that implicit solvation methods are more accurate than explicit solvation methods for free energy calculations?

I am looking for real data that concludes that implicit solvent models are definitively better than explicit solvent models for solvation free energy calculations. The motivation is a lovely reviewer ...
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