J. Ye jingyu... at gmail.com
Mon Dec 5 06:27:13 CET 2016

```Hi all,

I perform the frequency analysis for a periodic system. The results is a
little confused. I studied the similar post  "Question regarding frequency

Still have some questions.
1. When the frequency analysis performed for periodic system, the total
frequencies should have 3*N vibrational modes. Is it correct? However, if
the the frequency analysis performed for nonperiodic system, the total
frequencies should have 3*N-5/6 vibrational modes.

3. As shown in the following out put, I got 3*N vibrational modes for a
periodic system. How can I obtain rotational and translation modes?

2. What does the Cartesian Low frequencies mean ? What does the Internal
Low frequencies mean? The value after VIB| Cartesian Low frequencies (VIB|
Internal  Low frequencies) are the frequency modes?

VIB| Cartesian Low frequencies --- -9.8246    -0.68344     0.98510E-01
0.43250
VIB| Cartesian Low frequencies --- 0.51202     0.92096      1.5399
1.5930
VIB| Cartesian Low frequencies ---  1.8437
VIB| Frequencies after removal of the rotations and translations
VIB| Internal  Low frequencies --- -9.8246    -0.68344     0.98510E-01
0.43250
VIB| Internal  Low frequencies --- 0.51202     0.92096      1.5399
1.5930
VIB| Internal  Low frequencies ---  1.8437      2.0758      2.4938
2.6238
VIB| Internal  Low frequencies ---  3.0811      3.2091      3.3295
3.5402
VIB| Internal  Low frequencies ---  3.6433      3.7291      3.7916
3.9352
VIB| Internal  Low frequencies ---  4.2306      4.2991      4.5355
4.6211
VIB| Internal  Low frequencies ---  4.8689      5.0728      5.1608
5.2115
VIB| Internal  Low frequencies ---  5.4020      5.8929      5.9643
6.2709
VIB| Internal  Low frequencies ---  6.3279      6.4078      6.6109
6.7104
VIB| Internal  Low frequencies ---  6.9572      7.1510      7.1845
7.2941
VIB| Internal  Low frequencies ---  7.6242      7.7280      8.1031
8.1828
VIB| Internal  Low frequencies ---  8.3587      8.4853      8.5509
8.7804
VIB| Internal  Low frequencies ---  9.1584      9.2818      9.3660
9.8406
VIB| Internal  Low frequencies ---  9.9807      10.132      10.210
10.646
VIB| Internal  Low frequencies ---  10.811      11.460      12.629
13.013
VIB| Internal  Low frequencies ---  13.469      13.722      14.292
14.923
VIB| Internal  Low frequencies ---  15.063      15.481      15.892
16.260
VIB| Internal  Low frequencies ---  16.588      16.974      18.016
19.170
VIB| Internal  Low frequencies ---  21.897      26.041      28.454
31.464
VIB| Internal  Low frequencies ---  34.005      42.924      45.472
53.549
VIB| Internal  Low frequencies ---  101.18      194.93      195.81
204.28
VIB| Internal  Low frequencies ---  207.15      218.61      261.42
264.75
VIB| Internal  Low frequencies ---  279.02      279.99      282.28
284.04
VIB| Internal  Low frequencies ---  285.41      289.51      292.10
295.79

VIB|                        NORMAL MODES - CARTESIAN DISPLACEMENTS
VIB|
VIB|                         1                    2                    3
VIB|Frequency (cm^-1)  -687.927247          -181.440430
68.885130
VIB|Intensities           0.000000             0.000000
0.000000
VIB|Red.Masses (a.u.)     1.294491             5.311482
2.499368
VIB|Frc consts (a.u.)    -0.000742            -0.000015
0.000000
ATOM  EL             X     Y     Z        X     Y     Z        X     Y
Z
...............................

Thanks very much!

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