On 11/17/2013 05:16 AM, Caloma Trumica wrote: > In the manual of calculating electron-phonon interaction coefficients: > > http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide/node9.html > > Item 1 says that: "The latter MUST contain all [image: $ \bf k$] and [image: > $ \bf k$] + [image: $ \bf q$] grid points used in the subsequent > electron-phonon calculation" >
If I remember correctly, it's enough that an equivalent k+q+G point is found; where G is a vector of the reciprocal lattice. In order to guarantee this it's sufficient that the q point is one of the k points and that the k point grid is centered around Gamma. In more general terms, the q grid must be a subset of the k grid. I.e. if your q grid is composed by n1 x n2 x n3 points the k-point grid can be (n1*m1) x (n2*m2) x (n3*m3) where everything is integer. bests -- Dr. Lorenzo Paulatto IdR @ IMPMC -- CNRS & Universit? Paris 6 phone:+33 (0)1 44275 084 / skype: paulatz www: http://www-int.impmc.upmc.fr/~paulatto/ mail: 23-24/4?16 Bo?te courrier 115, 4 place Jussieu 75252 Paris C?dex 5
