question about frequency analysis

[J. Ye]

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 
analysis" https://groups.google.com/forum/#!searchin/cp2k/frequency$20analysis%7Csort:relevance/cp2k/_qNDNr2kfLM/iek1RiyIiQEJ. 

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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