This is an automatic expression generator program using wick's thoerem for quantum chemical theories. It produces expressions for electronic structure theories in the same form as derived by diagrams. This program can be used for unitary coupled cluster formalism.
All input are written in input.py and all latex form outtput expressions are generated in the latex.output.txt
Make sure you have Python installed. You may test the code through the file test.py which executes through Python test.py. It is written to go through simple examples of commutator operaration. Please further test the working of the code by generating all CCSD amplitude expressions by running test_ccsd.py.
- It is a string based program which produces final terms in the same form as in the diagram derivation (eg: \sum_{ijab}<ij||ab>t_{ij}^{ab}). The algorithm makes use of Wick's Theorem.
- The program can handle de-excitation operators in the commutator expressions, i.e, T^\dagger T contractions can be formed (these do not appear in coupled cluster theory).
- The program can work with commutator expressions such as [[V,T1],D1] and computes them recursively, innermost commutator first. The program has been tested for expressions upto third commutator. The features 2 and 3 make this program well suited for applications to unitary coupled cluster (UCC) formalism along with various coupled cluster based methods.