The Opacity Project
The name Opacity Project (OP)  refers to an international collaboration that was formed in 1984 to calculate the extensive atomic data required to estimate stellar envelope opacities and to compute Rosseland mean opacities and other related quantities. It involved research groups from France, Germany, the United Kingdom, the United States and Venezuela. The approach adopted by the OP to calculate opacities is based on a new formalism of the equation of state  and on the computation by ab initio methods of accurate atomic properties such as energy levels, f-values and photoionization cross sections . The OP final results are discussed by Seaton et al. .
OP opacities have been recently revised to include inner-shell contributions . The new data and a suite of easy-to-use codes to compute Rosseland means and radiative accelerations  can be downloaded as a tar file below.
* Opacity Tables: Ensembles of opacity tables for specific (pre-determined) composition using The Opacity Project data. The tables are in the OPAL format and can be used in stellar structure and evolutionary codes. All the routines allready in stellar evolutionary codes using OPAL tables will work with these tables (under construction).
* OPCD_3.3: Tar file (669 Mb) to be downloaded with complete package (data, codes, OPserver and instructions) for computing Rosseland mean opacities and radiative accelerations. Data files are the same as OPCD_2.0, but new software is included to install OPserver at the user's facilities (12-12-06).
* OPCD_3.3_opserver: Small tar file with the new software to install OPserver locally. Since the bulky OP data set with monochromatic opacities is not included, only the OPserver version that accesses data remotely from the Ohio Supercomputer Center will be operational (12-12-06).
* OPserver: An interactive server at the Ohio Supercomputer Center for online computing of opacities for arbitrary chemical mixtures. Codes have been updated with the release of OPCD_3.3 (12-12-06).
* TOPbase: online interactive database listing LS atomic data (energy levels, f-values and photoionisation cross sections) computed in the OP.
* OP Team
* Complete list of publications
* OPCD_2.1: Tar file (667 Mb) to be downloaded with complete package (data, codes and instructions) for computing Rosseland mean opacities and radiative accelerations. Data files are the same as OPCD_2.0, but new codes are included and some have been updated (01-03-05).
* OPCD_update_2.1: Small tar file to be downloaded with new codes to upgrade OPCD_2.0 to OPCD_2.1 (01-03-05).
* OPCD_2.0: Tar file (667 Mb) to be downloaded with complete package (data, codes and instructions) for computing Rosseland mean opacities and radiative accelerations (01-12-04).
1. The Opacity Project Team, 1995, The Opacity Project Vol. 1, Institute of Physics Publications, Bristol, UK
2. Hummer D.G., Mihalas D., 1988, ApJ 331, 794. Abstract
3. Seaton M.J., 1987, J. Phys. B 20, 6363. Abstract
4. Seaton M.J., Yu Yan, Mihalas D., Pradhan A.K., 1994, MNRAS 266, 805. Abstract
5. Badnell N.R., Bautista M.A., Butler K., Delahaye F., Mendoza C., Palmeri P., Zeippen C.J., Seaton M.J., 2005, MNRAS 360, Issue 2, 458. (Abstract).
6. Seaton M.J., 2005, MNRAS Letters 362, Issue 1, pp. L1-L3 (Abstract).