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GPOP - Quick Start step-1
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GPOP - Quick Start step-1

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


  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.


  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

(Skip this part if you do not like to learn about the intramolecular rotation right now.)
  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
        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
        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 Å2, 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.

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