Cmake fails with error: "Could not find compiler set in environment variable CC"

I am brand new to Linux/Ubuntu. I installed Ubuntu two days ago to run ROSS (Rensselaer's Optimistic Simulation System) developed by Argonne National Lab. However, I have been running into some build/installation process with CMake I can't seem to figure out.

I issue the following terminal commands up until the point I get an error:

git clone
cd ROSS
mkdir build
cd build
ARCH=x86_64 CC=mpicc CXX=mpicxx cmake -DCMAKE_INSTALL_PREFIX=../install ../

After the 5th command I get the error:

CMake Error at /usr/share/cmake-3.5/Modules/CMakeDetermineCCompiler.cmake:57 (message): Could not find compiler set in environment variable CC: mpicc.
Call Stack (most recent call first): CMakeLists.txt:1 (PROJECT)
CMake Error: CMAKE_C_COMPILER not set, after EnableLanguage
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!
See also "/home/lawrence/ROSS/build/CMakeFiles/CMakeOutput.log".

I have a feeling the solution to my problem is trivial but like I mentioned I'm brand new to Linux so I'd appreciate any help I can get and please go easy on me while describing the solution. Thanks!

Side Notes:

1. I installed CMake with:

   sudo apt-get install cmake & sudo apt-get upgrade

2. gcc and g++ is already installed

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