Atomic positions of strained Si lattice by adding Ge

[Vishal Tiwari]

Hi,

I am defining a bulk Si lattice and then I extract the atomic positions of Si lattice. After adding a fixed fraction of Ge into it, how can i get/extract new atomic positions of the strained lattice?

[Ulrik G. Vej-Hansen]

Would you like to calculate the new equilibrium lattice constant, or simply extract the coordinates? The latter is done in exactly the same way also after you substitute the Ge.

[Vishal Tiwari]

As i am replacing some Si atoms with Ge, this will introduce strain in the lattice and lead to atomic displacements of the original lattice positions. So, i need to extract the new atomic positions and the atomic displacements because of strain.

[Ulrik G. Vej-Hansen]

In that case, you need to do a GeometryOptimization with your chosen computational model, both before and after inserting the Ge. This procedure is described in the beginning of this tutorial: http://docs.quantumwise.com/tutorials/formation_energies.html

You can then get the coordinates directly from the output of the calculations or extract them from the BulkConfiguration afterwards.