# Questions tagged [free-energy]

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### How to compute molar Gibbs free energy (chemical potential) for single molecule using gaussian09?

I want to calculate the Gibbs free energy of single gas molecule (AsH3) using Gaussian 09, but I am confused between "Thermal correction to Gibbs Free Energy" and "Sum of electronic and ...
36 views

### Proof that equilibrium phase fraction(s) is a continuous function of composition

It seems that the equilibrium phase fractions (i.e., relative amounts of phase A1, A2, ..., Aq for a system in which there are q total phases) as a function of composition (for a constant pressure and ...
66 views

### How to calculate Gibbs free energy of a reaction involving cations using GFN2-xTB (via ORCA)

I am trying to compare the Gibbs free energy of reactions such as: A + 4K(+) --> B(4+) A + 4Na(+) --> C(4+) A + 4Li(+) --> D(4+) A + 4Ca(2+) --> E(8+) A + 4Mg(2+) --> F(8+) In these ...
117 views

### Why is potential energy used and not total energy when calculating free energy? [closed]

I have run a replica-exchange molecular dynamics simulation, using a number, $n$, of replicas initiated at the same number, $n$, of unique temperatures. I have calculated the free energy profile over ...
126 views

### Free energy calculation as a function of temperature over phase transition

I've run a molecular dynamics simulation (NVT) of a simple Lennard-Jones system of a few particles and I'm trying to calculate the Helmholtz free energy $\Delta F$ as a function of temperature over ...
185 views

### Free energy as a function of temperature over phase transition in molecular dynamics simulation

I've constructed a low density standard MD simulation (in Python), using the Lennard-Jones potential with an Andersen thermostat, of 10 particles in a box V = 10 $\times$ 10 $\times$ 10 in the NVT ...
1 vote
117 views

### Free energy calculations for lammps

Is there any tutorial or reference available to perform free energy calculations (umbrella sampling; thermodynamic integration; free energy perturbation; wisdom's particle insertion method) etc. with ...
48 views

### Free energy calculation

I want to plot the relationship between free energy and temperature. I want to consider two plots, when phonons are considered and when phonons are not considered how the free energy changes with ...
428 views

### Persistent errors in single equilibrium calculations (Thermo-Calc)

When running single point equilibrium calculations on an array of compositions I come across some compositions (for specific examples see below) that return the error ...
72 views

### What is the best model to calculate the free energies using ASE thermochemistry?

I am trying to calculate the free energy of adsorption of a small molecule on a 2D material. After adsorption, I am using the thermochemistry module of the Atomic Simulation Environment to calculate ...
127 views

### 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 ...
572 views

### How to calculate Gibbs free energy of adsorption at constant temperature with varying pressures

I want to calculate the Gibbs free energy of adsorption for an oxidized surface. The literature I consulted used the equations attached to this post. I am trying hard to find my way through. Any idea ...
103 views

### Potential of mean force from potential energy

Imagine a simple model of a crystal where every atom in the crystal is the same, and the potential energy of the pairwise interaction between atoms is some radial function of distance, U = U(r). For ...
516 views

### Thermo-Calc: how to suspend specific composition sets?

I am attempting to calculate the driving force of nucleation for several different precipitate phases using TC-Python. To this I want to suspend all phases, except for the matrix phase (e.g. FCC_L12). ...
224 views

### How to calculate phase regions using CALPHAD for higher order systems (>3 elements)?

I primarily use Thermo-Calc so I will use that to describe my problem but I am interested to hear general CALPHAD insight as well. Using Thermo-Calc I can quickly get an idea of the phase regions ...
56 views

### What is the meaning of a "free energy per unit surface area" vs "pressure" plot?

I don't understand this graph. From the graph, does it mean that at high pressures the oxide layer is stable and this stability reduces at low pressures and temperatures?
98 views

### What is the largest number of collective variables used in a metadynamics simulation?

Metadynamics is usually used to construct 1D or 2D free-energy surfaces. There seem to be a few examples for 3D free-energy surfaces: Paper 1: Exploring the Free Energy Landscape of Solutes Embedded ...
389 views

### Calculate deprotonation energy or Gibbs free energy of acids

I'm delving into the world of superacids, acids with an acid strength greater than that of sulfuric acid at 100%. I've recently encountered some computational papers which suggest that the ...
906 views

### Calculating enthalpy of a chemical reaction using DFT

Let's say we have a decomposition reaction $\tag{1}A \rightarrow B + C$ how would I go about calculating the Enthalpy of this chemical reaction using VASP. I am gonna describe what I am thinking below ...
149 views

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### What do phonon dispersion (or lattice dynamics) studies include?

I use the codes phonopy and phonopy-qha for phonon dispersion studies. phonopy-qha gives ...
205 views

### What information about a crystalline solid material goes into calculating phase diagrams in Thermo-Calc, and how?

Gibbs free energy, $G$, for a crystalline solid material could be described as: $$G\: =\: H_{T=0}\: +\: H_{T>0}\: +\: \text{ZPE}\: -\: T\cdot S,$$ Where $H$ is enthalpy, ...
236 views

### What thermodynamic data is collected in order to build a CALPHAD model?

To build a model using the CALPHAD approach, i.e. Gibbs free energy as a function of composition and temperature, typically taking the form of a Redlich-Kister polynomial, what kind of thermodynamic ...
469 views

### For a Thermo-Calc database, is it possible to view the equation/parameters of the Gibbs free energy models?

I want to get the equations that model free energy for a given phase in a given alloy system (see attached image). I do not just want to get values of free energy for specific compositions. Is it ...
218 views

### What are the methods for calculating solvation effects in free energies and how do they compare?

I've just found this paper (J. Chem. Phys. 141, 174106 (2014)) that deals with the translational and rotational entropies in solution. The method is promising but, unfortunately, requires a ...
426 views

### Are there any MD packages that do proper free energy sampling in the NPT ensemble?

Statistical Mechanics is the basis of molecular level calculations of properties and averages. Nowadays free energy calculations are fairly "turn-the-crank", which is not necessarily a good ...
2k 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 ...
487 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 ...