Dear Du, the input you found below is to extract the U values from a series of scf calculations. You can give a look (besides the reference cited below) to the tutorials you find in this webpage: http://www.quantum-espresso.org/wiki/index.php/QESB09. Unfrtunately the value of U is generally not portable and changes depending on the invironment of the atom in the specific crystal you are considering. the one you cite is a good example: Fe in bulk Fe and in FeO. So in principles we need to recompute it each time.
hope this helps. Matteo duchl06 wrote: > dear pw users > i want to do a calculation of V chain absorb on a plane with DFT+U, > but i donot know how to determine the value of U. > i found a PPT on the pwscf's media site, they said the value of U > could be decised by a linear response approach. > but i really donot understand that like the input file resp_mat.in > > &input_mat > ntyp = 1 # number of types of atoms > na(1) = 2 # number of atoms per type > if we have different type atoms with different number, how we set these? > > nalfa = 5 # number of perturbations (alpha) > filepos = 'pos_sc1' # file containing the atomic positions and the > vectors of the unit cell > back = 'neutral' # to add a neutralizing ??background??. see PRB 71 > 35105 (2005) > what does this mean > filednda = 'file_sc1' # file containing the names of the files dn*dat > n1 = 4 > n2 = 4 # number of unit cells in each direction to construct the > supercell for > n3 = 4 # extrapolation (in this case a 4x4x4 supercell of the SC one) > &end > > and they get the U is about 2.4ev for the iron, and they use 4.3ev for > the FeO calculation, > we always need a linear response approach to get the U for every system > or just a U for a certain pseudopotential (i mean if we get a U for V > bulk, then if i could use this value for another system with V atom, > like V2O3 etc.) > any suggestions or comment would be OK. > thanks > > Du > xiaguanying university > > > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
