6. Opacity and its derivatives
We recomputed many thermodynamic quantities and the opacities in the process of preparing the models for input to the nonadiabatic oscillation package. Every effort has been made to be consistent with the procedures followed in the evolution code. The most tricky operation at this point is the determination of accurate opacity derivatives. The opacities are interpolated linearly and smoothed locally in the evolution code. As first and second derivatives of the opacity are needed in the oscillation package a more refined interpolation procedure had to be adopted to guarantee smoother derivatives. We chose the Houdek (Houdek & Rogl 1996) routines which use two-dimensional rational splines. For each mesh point of the models we constructed a opacity grid in the plane in which the splines were fitted and the opacity derivatives were determined.
© European Southern Observatory (ESO) 2000
Online publication: August 17, 2000