Does anyone have experience in calculating the density of states (DOS) from the velocity autocorrelation function (VACF)? The DOS is defined as the fourier transform of the VACF from
gw = integral (cos(wt)*VACF(t)dt)
however when I use a 1D FFT algorithm the DOS has both real and imaginary components as the result of the transform. Here’s the question that I have: is the DOS the magnitude of the transform? the magnitude squared? or just the real part (because the expression of the transform has the cos(wt) term).