cc4x is a canoncial coupled cluster calculations code. It uses tensor contraction libraries for the occurrent tensor operations. Currently, only CTF (cyclops) is supported. However, adding other contraction libraries is straightforward (see TensorBackend.md). The offered functionalities are limited! Please check out cc4s for general survey.

You will need yaml-cpp and cyclops. Both can be found on github.

When running the uniform electron gas, a well known model system in solid state physics, no input files are required. Reasonal input parameters can be found in the work of Morales and co-workers afqmc-ueg. Furthermore, the input files from cc4s can be used (with tiny modifications in the yaml).

Go to the file etc/cc4x.mk and define the CTF_PATH and YAML_PATH. Then go to root directory and type make. This build system assumes gcc compiler with openmpi and OpenBlas.

You might want to start running the BN test provided in the test directory. You should be able to reproduce the CCSD energy, calculated with cc4s. Simply run cc4x: $cc4x -i 40 If you want to run some (large scale) calculations on the uniform electron gas. For instance $cc4x -o 27 -v 224 -r 1 Note that the value of r will have no effect on the performance of the calculation (simply choose a positiv value; 1.0 is fine). Have a look at cc4s-manual for some large scale calculations of cc4s.