16 votes

How to explain to a five year old why "DFT with local exchange–correlation functionals do(es) not describe van der Waals interactions accurately"?

Standard DFT functionals are based exclusively on local information, e.g. for a GGA functional $$ E_{xc} = \int n({\bf r}) \epsilon_{xc}(n({\bf r}), \nabla n({\bf r})) {\rm d}^3r $$ while van der ...
  • 15.1k
10 votes

How to explain to a five year old why "DFT with local exchange–correlation functionals do(es) not describe van der Waals interactions accurately"?

I'll turn my comment as an answer, as requested by the OP and Nike. Susi Lehtola's answer has already pointed out that dispersion (which may be a more accurate term than van der Waals interaction here)...
  • 7,463
5 votes

Help with understanding topologically-protected edge states in domain wall systems

I think my understanding on this problem has improved somewhat. Let me try to clarify my confusions. If anyone sees issues with this reasoning, please let me know. The idea of phases in this context ...
4 votes

Wavefunction magnitudes being degenerate everywhere on parameter space even though energy degeneracies occur at isolated points?

This is a somewhat handwaving answer but I think it gets the main point across: We should start by pointing out that the two components of your eigenstates represent the wave function amplitudes on ...

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