A New Open-Source Nuclear Equation of State Framework based on the Liquid-Drop Model with Skyrme Interaction

André da Silva Schneider, Luke F. Roberts, Christian D. Ott

Available on Phys. Rev. C and arXiv!


The equation of state (EOS) of dense matter is an essential ingredient for numerical simulations of core-collapse supernovae and neutron star mergers. The properties of matter near and above nuclear saturation density are uncertain, which translates into uncertainties in astrophysical simulations and their multi-messenger signatures. Therefore, a wide range of EOSs spanning the allowed range of nuclear interactions are necessary for determining the sensitivity of these astrophysical phenomena and their signatures to variations in input microphysics. We present a new set of finite temperature EOSs based on experimentally allowed Skyrme forces. We employ a liquid drop model of nuclei to capture the non-uniform phase of nuclear matter at sub-saturation density, which is blended into a nuclear statistical equilibrium EOS at lower densities. We also provide a new, open-source code for calculating EOSs for arbitrary Skyrme parametrizations. We then study the effects of different Skyrme parametrizations on thermodynamical properties of dense astrophysical matter, the neutron star mass-radius relationship, and the core collapse of 15 and 40 solar mass stars.


SRO EOS Source Code

The SRO source code is released as open source under GPLv3. It is available from the following Bitbucket repository:

The master branch of this repository is the stable code that we recommend to the user. Along with the code comes an extensive user guide:

If you run into problems using the code or have other questions or comments, please feel free to contact us at SROEOS __at__ We hope that you will find our code useful! Please feel free to send us bugfixes and any physics improvements that we can incorporate in future version. Also, please make reference to our paper should you use our code and resulting EOS tables in published work.

EOS Driver and Interpolation Routines

The SRO EOS tables use the same overall HDF5 format introduced with the tables of O'Connor & Ott that are available at However, as you will be able to gather from the User Guide, the SRO tables contain additional quantities. The standard driver and interpolation routines that we provide below are not set up to handle these. So should you need the new additional quantities, minor code changes are necessary. Also note that there is a difference in the definition of the speed of sound between our tables and those of O'Connor & Ott. We address this in Section 7 of the User Guide.

EOS driver and interpolation routines for Fortran 90+: These routines are very old, not tuned for performance, and we do not recommend their use in a production code. They are available here:

The much better C/C++ routines are available here:

SRO EOS Tables

We provide a set of pre-made EOS tables for the impatient user. We use the table ranges and resolution given in Table VI of our SRO EOS paper. For each parametrization, we provide pure SNA and SNA+NSE tables. All tables include photons, electrons, and positrons. Note that the tables are bz2 compressed must be decompressed before use. The standard resolution tables are about 550 MB in compressed state.


EOS Variant Download link
KDE0v1 with NSE (3335 nuclides)
KDE0v1 pure SNA
LNS with NSE (3335 nuclides)
LNS pure SNA
LS220 with NSE (3335 nuclides)
LS220 pure SNA
LS220star with NSE (3335 nuclides)
LS220star pure SNA
NRAPR with NSE (3335 nuclides)
SKRA with NSE (3335 nuclides)
SkT1 with NSE (3335 nuclides)
SkT1 pure SNA
SkT1star with NSE (3335 nuclides), high resolution
SkT1star pure SNA, high resolution
SkT1star_3335_rho781_temp325_ye131.h5.bz2 (4.5 GB!)
SkT1star_0000_rho781_temp325_ye131.h5.bz2 (4.3 GB!)
SkT1star with NSE (3335 nuclides)
SkT1star pure SNA
Skxs20 with NSE (3335 nuclides)
Skxs20 pure SNA
SLy4 with NSE (3335 nuclides)
SLy4 pure SNA
SQMC700 with NSE (3335 nuclides)
SQMC700 pure SNA



This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico under award 201432/2014-5 and by the US National Science Foundation under awards TCAN AST-1333520, CAREER PHY-1151197, and PHY-1404569. Note that our new EOS framework was one of the core deliverables of the TCAN grant.