Dear Lorenzo Paulatto, Can the finite size as a perturbation with Green function methods be added to pw.x calculations too ? For example can the Self-consistent field energy calculated for unit cell be modified with the Green function methods to that of a finite sized crystal ?
Regards, Krishnendu ------------------------------------------------------------------- > On 25 Dec 2022, at 00:26, Md. Jahid Hasan Sagor < [ > https://lists.quantum-espresso.org/mailman/listinfo/users | md.sagor at > maine.edu ] > wrote: > > > Then why would the calculation be considered > computationally large if I define 10 nm width ( rather I reduce my system > size from infinite to 10 nm)? Can you explain it to me? Because “reducing the > size” (actually, making it finite) would break translational symmetry and > thus prevent us from using the Bloch theorem. In an infinite *and periodic* > system, Bloch theorem allows us to break an infinite-dimensional Hamiltonian > matrix into an infinite number of finite-dimensional matrices (one for every > k vector), which can be easily diagonalized one by one. This is not possible > in a finite system (or in an infinite and aperiodic one, for that matter). > So, surprisingly (or not so surprisingly once you understand the maths) > finite systems may be computationally harder than some infinite ones. Stefano > B ___ Stefano Baroni, Trieste -- [ http://stefano.baroni.me/ | http://stefano.baroni.me ] * Previous message: [ https://lists.quantum-espresso.org/pipermail/users/2022-December/049959.html | [QE-users] Phonon Dispersion of graphene ]
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