Based on this and some other literature I take it that the number of phonon modes is contingent upon the size of the unit cell. I also understand that in using Quantum ESPRESSO, the study of defects necessitates a larger unit cell to bypass the periodic boundary conditions. My question is that if...

When experimentally reported lattice constants (a,b,c) are known, is it correct to only vary atomic positions and keep (experimental) lattice constants unchanged in structure optimization? Doing this, there must be a non-neglectable external pressure acting on the final structure as it must not b...

I am performing phonon calculations ph.x of CsPbBr3 primitive cell in QE v7.2 and it is taking a long time on 6 6 6q-points and 8 8 8 k-points. Questions Can we make just the gamma point phonon calculations instead of the entire grid? Is there any way to reduce computation time? Can we use Wannie...

How does the size of atoms within a structure influence the speed of DFT (Density Functional Theory) calculations? considering that the calculation speed is known to scale cubically with the number of atoms? If I aim to estimate the calculation speed of two systems with different types of atoms b...