update readme with citation and pointer to PelePhysics (#24)

* update readme with citation and pointer to PelePhysics

* update README

---------

Co-authored-by: w0g <gew1@ornl.gov>

README.md

@@ -4,14 +4,20 @@
 [![AMReX Badge](https://img.shields.io/static/v1?label=%22powered%20by%22&message=%22AMReX%22&color=%22blue%22)](https://amrex-codes.github.io/amrex/)
 [![Exascale Computing Project](https://img.shields.io/badge/supported%20by-ECP-blue)](https://www.exascaleproject.org/research-project/combustion-pele/)
 
+# WARNING
+
+The production version of PeleRad have been moved to [PelePhysics](https://github.com/AMReX-Combustion/PelePhysics) and this repository is now only for experimental developments.
+Further development is continuing within PelePhysics. The tests are in PelePhysics, while the example cases are part of PeleLMeX.
+
 ## Table of Contents
 - [Description](#description)
 - [Installation](#installation)
 - [Usage](#usage)
 - [License](#license)
+- [Citation](#citation)
 
 ## Description
-PeleRad is a module for modeling radiative transfer in reacting flows. It supports GPU performance portability and adaptive mesh refinement through AMReX and is coupled to PeleLMeX.
+PeleRad was a module for modeling radiative transfer in reacting flows. It supports GPU performance portability and adaptive mesh refinement through AMReX and is coupled to PeleLMeX.
 
 ## Installation
 1. Clone the repository: `git clone https://github.com/AMReX-Combustion/PeleRad.git`
@@ -22,7 +28,7 @@ To build with the PeleLMeX flow solver, GNUMake is prefered.
 One example script to build a test case on Frontier is provided in the '/scripts' folder.
 
 To run the script:
-'./build_PeleLMeX_Fontier.sh' 
+'./build_PeleLMeX_Fontier.sh'
 
 ## Usage
 PeleRad is designed for modeling radiative transfer in reacting flows. To activate and use PeleRad in conjunction with PeleLMeX, follow these steps:
@@ -35,4 +41,14 @@ PeleRad is designed for modeling radiative transfer in reacting flows. To activa
 The license file is located at
 https://github.com/AMReX-Combustion/PeleMP/blob/master/license.txt
 
-
+## Citation
+To cite PeleMP, please use the following [Journal of Fluids Engineering article](https://doi.org/10.1115/1.4064494):
+```
+@article{owen2023pelemp,
+  title={PeleMP: The Multiphysics Solver for the Combustion Pele Adaptive Mesh Refinement Code Suite},
+  author={Owen, Landon D and Ge, Wenjun and Rieth, Martin and Arienti, Marco and Esclapez, Lucas and S Soriano, Bruno and Mueller, Michael E and Day, Marc and Sankaran, Ramanan and Chen, Jacqueline H},
+  journal={Journal of Fluids Engineering},
+  pages={1--41},
+  year={2023}
+}
+```