# Tag Info

### Exploring Elastic Constants Calculation in VASP: Methods and Best Practices

Theoretical Background: Elastic constants can be calcualted in one of two approaches. First is via the stress-strain relationship, and the second is by strain-energy relationship. First approach: In ...
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### How to use the ev.x tool in Quantum ESPRESSO?

This answer is partly based on the Computational Materials Physics Course by Stefaan Cottenier. Follow the steps provided below: Prepare a text file with two columns, the first column being the unit ...
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### How can we make a mechanically unstable cubic system, stable

Depending on your calculation and how much time you want to invest in getting the best property you can, I suggest two different approaches to make this system stable: Fully relax the geometry of the ...
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### Elastic constants calculation

The Elastic constants are calculated within vasp using IBRION=6 and ISIF=3. The Elastic constants are calculated from stress-strain relationship by applying finite distortion of lattice and ions. ...
• 4,128

### elastic constants transformation/basis change P21/a -> P21/n

In order to define the matrix transforming the P21/n structure into P21/a it is imperative to know the unique axis of both space groups. For example the contracted P21/n symbol can be used for the ...
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Accepted

### Elastic properties of graphene by using DFT (Quantum espresso)

The elastic stiffness $C_{j}$ with respect to each $j$ direction mediates the energy $E$ at a deformed structure and the mechanical strain $\epsilon_{j}$ as follows [Mir, S. H. et al. ACS Omega. 2020, ...
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### How can I calculate the elastic properties of a unit cell and a supercell?

There is new tool called ElasTool. It is a Python-based toolkit for computing the second-order elastic constants (SOECs) and mechanical properties of crystal systems. It is designed to integrate with ...
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### 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: ...
• 176
Accepted

### How to start with the elastic properties of 2D materials using the VASP code?

Elastic constants can be derived from constitutive relationship by calculating stresses from a strained system $$\sigma_{ij}=C_{ijkl}\epsilon_{kl}$$ Once the crystal is deformed by some finite strain ...
• 4,128
Accepted

### What is the difference between elastic and mechanical properties of materials?

When we talk about mechanical properties, we generally refer to response of the material on application of external load. Apart from external load, responses can be of mixed nature, such as thermo-...
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### How to do a proper relaxation of the multicomponent structure?

A few things: If you start with your supercell of pure bcc Ti, the spacegroup symmetry will be Im-3m, as expected. As soon as you replace one or a few atoms of Ti with Nb, or any different species, ...
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### How to calculate 2D elastic constants of boron nitride monolayers from uniaxial strains?

I think you should take a rectangular unit cell instead of the hexagonal unit cell depending on this article (The response of mechanical and electronic properties of graphene to the elastic strain M. ...