# Tag Info

Accepted

### The Appearance of Imaginary Frequencies in Lattice Vibration Calculations with Increasing KPOINTS

In the usual perturbation theory approach, we optimise a structure to minimise the forces (to zero, within some small tolerance) and obtain the ground state structure (or a local energy minimum). ...
Accepted

### How can I perform a cell shape relaxation in a specified direction using VASP?

As of July 2023 at least, VASP doesn't have such a functionality (see this post). I know of two options (I've used the first one frequently when relaxing slab structures while keeping the vacuum axis ...
Accepted

### Optimal choice between ISIF = 3 and ISIF = 4 for lattice parameter and atomic position relaxation in VASP calculations

You've already summarized the differences in your question, but to be complete: ISIF=3 has an additional degree of freedom that allows the cell volume to change. In principle, there should be no ...

### Fitting of Brich-Murnaghan equation of state

If you know Julia, I have a package called EquationsOfStateOfSolids.jl that is designed to do this. It currently can fit and evaluate $E(V)$, $P(V)$, and $B(V)$ on several equations of state: ...
Accepted

### Can the the relaxed energy of a material system (eV/atom) computed by DFT using VASP be positive?

When DFT is being used for electronic structure energy calculations, a negative energy would be indicative of bound electrons. There's nothing physically, chemically or mathematically illegal about ...

### Can the the relaxed energy of a material system (eV/atom) computed by DFT using VASP be positive?

Firstly, by expressing the energy per atom (eV/atom), it allows for a more convenient comparison between different materials or systems, as it provides a measure of the energy on a per-atom basis. ...
Accepted

### Random velocity generation

You can use ASE to generate the required random velocities, you may refer to this sample code to achieve this taks: ...

### Adsorption of Li on GeC (optimization problem)

The adsorption energy of Li or K atoms on a GeC sheet is influenced by several factors, including the electronic structure, bonding interactions, and surface reactivity of the materials involved. If ...

### Fitting of Brich-Murnaghan equation of state

Here are some references from my own work: a script that reads energy-volume data from a csv file and fits a Vinet equation of state: https://github.com/flokno/tools.mlff/blob/main/mlfftools/scripts/...

### Calculation of charge defect formation energy

First, the energy correction term, $E_{corr}$. It arises due to presence of periodic boundary conditions (defects are spuriously repeated) and of background charge compensation (hidden from the user). ...

### How to define a mesoporous material in VASP (introducing the vacuum gap)

First we can start by converting the struture generated with LAMMPS into POSCAR file format In this case, you can use cfg file format to dump the frames from LAMMPS, which will write the atom types, ...