Followings are examples of the usage of GPOP tools for examination of intramolecular rotation etc.

Preparation

1. Build GPOP from source files or unpack pre-built binaries for Windows according to the instructions in Installation section.
2. Set PATH to the directory where GPOP executables reside.   Then, change directory to the gpop/sample.
3. Alternatively, if you found any difficulty in setting PATH, copy all GPOP executables (in gpop-win32-binary) and all sample files (in gpop/sample) to the current directory.

Pre-processing

1. Execute gpop1scf for etp500.log by typing:
   gpop1scf etp500
2. Files etp500.gpo and etp500.mod (or etp500_.mod) must have been created in the current directory.
3. The file, etp500.gpo, is a GPOP format file containing essential results extracted from etp500.log. A GPOP format file is an ASCII text file and may be viewed with text editors. This file only may be usefull for some purposes: for example, the value of SCFenergy key in jobInfos block is the final SCF/DFT energy at optimized geometry.

Calculation of properties of an intramolecular rotation

1. Execute gpop6irt as;
   gpop6irt etp500 8-9 1-@
2. Calculation is made for intramolecular rotation around C[1]–O[8] bond of the ethyl peroxy radical shown below.
   
3. The properties of the intramolecular rotation specified in the command line are printed to the standard output as follows:

   base file name: etp500
   moiety-1: 8-9
   moiety-2: 1-2-3-4-5-6-7
   two moieties are whole molecule.
   dihedral angle between moieties 1 and 2: 71.4081
   [moiety-1]
       appI[amuA2]: 24.05850766
       appB[cm-1]: 0.70069305
    --- symmetric top ---
    symRedI[amuA2]: 6.66957233
    symRedB[cm-1]: 2.52754274
    --- asymmetric top ---
    asmRedI[amuA2]: 7.46994390
    asmRedB[cm-1]: 2.25672767
   [moiety-2]
       appI[amuA2]: 37.50552344
       appB[cm-1]: 0.44947057
    --- symmetric top ---
    symRedI[amuA2]: -4.75414496
    symRedB[cm-1]: -3.54588033
    --- asymmetric top ---
    asmRedI[amuA2]: 7.46994389
    asmRedB[cm-1]: 2.25672767
   [most resembling vibrations]
    mode-001: 0.99820037
    mode-010: 0.53138804
    mode-004: 0.46718380
    mode-009: 0.29262286
    mode-020: 0.24449702

   
   
4. In most cases, the required results can be found in the last of [moiety-1] section. The reduced moment of inertia for rotation around C–O bond is 7.470 amu Ų, or the corresponding rotational constant is 2.257 cm^–1. Also the last [most resembling vibrations] section indicate that the rotation around C–O bond well resembles the vibrational mode #1.