Gaussian: Tutorial on Water Single Point Energy and Scripts

Introduction

You can use a script to create and save a Gaussian file based on restricted Hartree-Fock calculations on a 6-31G(d) basis set for water single point energy.

Tutorial Steps

Use your favorite editor to create a script file with the following lines and save the file as “spe_hf_6-31g-3”. Water molecule is described in the form of Z-matrix in the following C shell script file.

  #!/bin/csh 
  g98 << END > spe_hf_6-31g-3.log 
  #T HF/6-31G(d) Pop=Reg Test 
  Water HF Single Point Energy with 6-31G(d) Basis Set
  0 1 
  O 
  H,1,R2 H,1,R3,2,A3 
  variables: 
  R2=0.96 R3=0.95990885 
  A3=109.4731442 
  ----Blank Line----
  END 
  echo "Job Done. "

#T requests terse output from the program (only the essential results). If # alone, normal (traditional) Gaussian output is requested. A restricted ( R) Hartree-Fock ( HF) calculation using the 6-31G(d) ( 6-31G(d))basis set is chosen. Pop=Reg asks to display highest five occupied and lowest five virtual molecular orbitals and other information not included in the output by default. Test will prevent Gaussian from entering this job’s results into the site archive. A blank line after the #T line is a one-line description of the calculation. After another blank line, the water molecule is then specified. The first line of the molecule specifications gives the charge and spin multiplicity for the molecule as two free-format integers. For water, the molecule is neutral (charge 0) and has spin multiplicity 1 (singlet). Then, the water molecule is represented by Z-matrix format. Notice that there is a blank line at the end of the file.

After the file is created, file permission needs to be changed to include executable. Type the following command to achieve that.

  chmod 755 spe_hf_6-31g-3 

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