Make the Input Files

Questions:

• What input files are required, and what should they contain?
• What's a block? Can we have blank blocks in the input files?
• What's the difference between ``1.'' and ``1''?
• Are the input files case sensitive?
• Are comments allowed?
• What kind of whitespace can I include in the input files?
• Are file paths absolute or relative?
• Can we dereference environment variables?

Things to know beforehand:

• How to use a unix text editor to create and edit files.

Now, we need to create our input files, which will tell the program what to do for us. There are two mandatory files required to do a basic calculation: a CNTL file and a STRC file. Their filenames should end with a .cntl and .strc suffix respectively. The prefix of the filenames should be the same, probably the name of the system to be studied. It's also a good idea to organize each system to be studied into it's own directory. For this tutorial, we will first look at a molecular system, formaldehyde (H₂CO).

1.

Define a name for the system, like ``h2co''.

2.

Create a directory where you will place the input files and change to that directory. This is also where you will run the system and get the output, so make sure you have enough free disk space in your quota or use a scratch area. I am putting it in my home directory:

alpha:~> mkdir tutorial/h2co

alpha:~> cd tutorial/h2co

alpha:~/tutorial/h2co>