Editing G09 (section)

== MECP calculations (Old Prof. Harvey version) ==

To find Minimum Energy Crossing Points in Gaussian you can use the program developed by Prof. Jeremy Noel Harvey. To use the program for first time you will need a bit of patience.

1.- Download the program from the repository:

* Connect to the repository: http://aliga.iciq.es/fsn/ ask Martín for the username and password.
* Go to the directory /Gaussian/MECP/ and copy all files and directories into a new directory in your home.

2.- There are two directories the PROGRAM and the SHELL. There is also a "README" file that can help if you follow the instructions carefully, and another file called "envia" which is a submitting script.

2.1.- In the PROGRAM directory you will find the fortran program, there you have to '''compile''' the program every time that the '''number of atoms''' of your system changes. That is done by:
* Delete all *.o files and the MECP.x file, 
* Edit the file MainProgram.f: Change the value of the variable Natom, that is change number 5 in the line "parameter (Natom=5)" by the number of atoms of your system. 
* Re-compile the program by typing "make". This will generate a new version of the executable file MECP.x. 
* Copy the MECP.x generated in the directory you want to work in.

2.2.- In the SHELL directory there is a number of files you will need to mount your system. Copy all of them to your working directory. Go to your working directory and start editing the files:
* Change the number of atoms in files first_progfile and master_script.
* Add your starting geometry in the file geom. The geometry should be in the same format as in the model file: number of the element and xyz.
* Read the file geom in the file first_progfile.
* Copy the first_progfile to ProgFile. The first_progfile will not be changed along the calculation but the ProgFile will.
* Edit the 'Input_Header_A' and 'Input_Header_B' according to your methodology requirements. One Input_Header for each spin state. They should have different names for the .chk files.
* Use the 'footer' file to include the basis sets if necessary.
* Once the Input_Header files, the geom and the footer are ready type "csh -f Make_First_Inputs" to generate automatically the first input files: Job0_A.gjf and Job0_B.gjf. If you don't have the .chk files available, open the two input files Job0_A.gjf and Job0_B.gjf  and delete "guess(read)".
* Submit the calculations with a submitting script. I use the "envia" file you will find in the main directory. Please edit the "envia" file according to the machines you want to use. To submit it to the queue just type "qsub envia".

3.- If you do not use DFT or you have special needs you might have to change the extract_energy or extract_gradient files by the ones available in the SHELL directory, or the main_script file.