Program for the computation of MECP using the Firefly Quantum Chemistry program
Abstract
Minimum-energy crossing points (MECP) between potential energy surfaces with different spin multiplicities are important in non-radiative relaxation of excited states, analysis of phosphorescent materials and for the study of "spin-forbidden" reactions. Harvey et al. described an algorithm that you can use to find MECP using any theory level, in J.N.Harvey, M.Aschi, H.Schwarz, W.Koch (1998) The Singlet and Triplet State of Phenyl Cation. A Hybrid Approach for Locating Minimum Energy Crossing Points between Non-interacting Potential Energy Surfaces. Theor. Chem. Acc. 99, 95 Prof. Harvey kindly provided me with the code, which I have adapted for use with the output from the quantum-chemistry program Firefly (Alex Granovsky, Moscow State University, http://classic.chem.msu.su/gran/gamess/index.html). Three files are provided: mecp.c - program code , in C mecp - compiled version (ubuntu) MECP_script - self-explanatory mecp requires output and punch files from two calculations of the same system, with the same coordinates, but different spin multiplicities. These files MUST be named as: First.out and First.dat (for the first spin multiplicity, i.e. that with the HIGHER energy ) Second.out and Second.dat (for the second spin multiplicity) mecp produces several output files: results.txt (geometries, graidents, energies, etc...) results.xyz (geometries in xyz format) new_geom.txt (the next geometry in the MECP optimization) new_grad.txt (computed gradient - output only when BFGS…
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