Dear All, I am interested in calculating various matrix elements between eigenfunctions, but first I am trying to see if I can calculate the norm of a eigenfunction. I am able to do the integration in the muffin tins. I checked the values I get with the numbers in case.qtl, and they match for each atom. However, I am having problems getting the right number for the interstitial part. To do the integration in the interstitial, I perform following steps:
1) Read the K-vectors and corresponding coefficients for a particular k-point and band number. 2) Set up a FFT grid (using the fft dimensions from case.output2) and put the coefficients in a FFT array with zero where coeff for a K point is not specified. 3) Set up step function U using the algorithm specified in rean0.f 4) Fourier transform FFT and U to real space using c3fft. 5) set FFT(i1,i2,i3) = conjg(FFT(i1,i2,i3)) * FFT(i1,i2,i3) * U(i1,i2,i3) 6) Back Fourier transform FFT. 7) Renormalize by dividing by the dimension of FFT and volume of the unit cell. 8) FFT(1,1,1) should be the desired integral. I think there is something wrong with renormalization because for degenerate bands, I get the same value for the integral. But renormalization constant is different for different set of degenerate bands :-/ To check if the coefficients are stored only for one element of star of K, I did calculation with no symmetry, too. In particular I did CsCl with 1_P1 and Pm-3m symmetries. In both cases the number of coefficients calculated were the same (347 coeffs when RK-max = 7 and Gmax = 12). I tried to look how the interstitial part is calculated for case.qtl. The corresponding code seems to be in outp.f. But it is simply 1 - spherical part (line 223 in outp.f: TCOUT=100.D0-TC) I would be extremely grateful if anyone can point me to the right direction. Thank you, Alaska