6

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 structure. Some comments below your question suggest that you tried to fully relax your structure, but the structure is probably not fully relaxed if it is ...


5

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 cell volume (a.u^3 or Å^3) of each of your calculations, the second column being the corresponding total energy (Ry). Type ev.x in the terminal, which will ask ...


4

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 full P21/n11 symbol (unique monoclinic axis along a), for the full P121/n1 (unique axis along b) and for the full P1121/n (unique axis along c). The same apply for ...


4

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, you are breaking symmetries and the symmetry will be lowered. Marker et al. computed elastic properties for bcc Ti-X (X=Mo,Nb,Ta,Zr,Sn) and handled the lower ...


2

Elastic constants can be calculated using two approach, one with Energy-strain relationship and another with stress-strain relationship. The key ingredient in above two methods is energy or stress at particular mode of distortion. For example in cubic crystal which have 3 fold symmetry about body diagonal need three independent elastic parameters to define ...


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