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.   The setpath.bat, setpath.csh, and setpath.sh in the sample folder may be usefull for this purpose.   Then, change directory to the gpop/sample.
3. Alternatively, if you found any difficulty in setting PATH, copy all GPOP executables (in gpop-winXX-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.