MECPy implements the algorithm of MECP optimization proposed by Jeremy Harvey with co-workers (Harvey, J. N.; Aschi, M.; Schwarz, H. & Koch, W. "The singlet and triplet states of phenyl cation. A hybrid approach for locating minimum energy crossing points between non-interacting potential energy surfaces" Theor. Chem. Acc., 1998, 99, 95–99)
It can optionaly use redundant internal coordinates automatically generated using the algorithm descibed Bakken and Helgaker (Bakken, V. & Helgaker, T. "The efficient optimization of molecular geometries using redundant internal coordinates" J. Chem. Phys., 2002, 117, 9160). By default it uses Cartesian coordinates.
MECPy is a Python code requiring an external quantum-chemical program to compute energies and gradients. MECPy is currently interfaced with Turbomole, Gaussian09 and NWChem. It is possible to interface it with other programs.
If you are interested in MECPy, please contact the author by email.