# A NRG calculation

1. Aug 24, 2016

Hi there! I've recently performed and NRG code to study one impurity model, related to the Anderson model. I want to calculate the density of states (spectral function) but I dont know if I am doing things right.

Since after some iterations we need to truncate the number of eigenstates of the hamiltonian, these are the only ones contributing to the next iteration. Since the hopping parameters of the Wilson chain decay exponentially, at each iteration there is a characteristic frecuency (omega) of the order of the hopping parameter for that Nth step.

My question is, when evaluating the density of states (on the impurity), we have the formula for T=0 of the matrix elements of the impurity operator, multiplied by Dirac delta functions. So each peak is multiplied by a "weight" given for that matrix elements squared. I am passing these delta functions to gaussian functions, whose width is of the order of the characteristic frecuency, but for each eigenstate, only evaluating these gaussians at w = 2wN, being wN the characteristic frecuency, is that alright¿ Thanks in advance

2. Aug 29, 2016