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如何计算分子的频率、红外、零点能、转动能量、转动惯量、熵、焓、热熔与Gibbs自由能

1,优化分子结构

2,导入优化好的坐标到ADFinput中,并设置参数如下图

关于热力学性质的计算参数如下:第一个参数为压强,第二、三个参数是关心的温度范围,例如这里希望关心298.15K、299.15K……398.15K总共101个温度的热力学性质,因此设置参数如下:

3,保存、运行

4,结果查看

在该任何相关的任何窗口,或在ADFjobs中选中该任务之后,点击ADF LOGO > Spectra,即显示振动频率:

如果有虚频,则虚频的峰为负数,此例中没有虚频。点击峰的位置,或者下方列表中计算得到的三个峰的三行,则显示该峰对应的振动模式的振动动画。

点击SCM > Output > Other Properties > Zero-Point Energy可以看到零点能。

在ADF logo > Output >Other properties > Intensities Collected,可以看到文本形式的输出内容,包括强度和热力学信息:

 Statistical Thermal Analysis  ***  ideal gas assumed  ***

  
 Pressure:                  1.000000 atm.

 Lowest Temperature:      298.150000 K
 Highest Temperature:     398.150000 K
 Nr. of T-steps:          101



 Moments of Inertia [amu*bohr^2] and principal axis
 ==================================================

           1.9638          4.4225          6.3862
 ------------------------------------------------
           0.0000          0.0000          1.0000
           1.0000          0.0000          0.0000
           0.0000          1.0000          0.0000


 The rotational contribution to the molecular entropy includes
 a term, dependent on the symmetry number sigma. The results 
 reported below were computed using sigma = 2, determined from
 the point group symmetry of the input geometry (C(2V)). 
 If this is not the correct symmetry, try symmetrizing the molecule before
 running the calculation (note: linear molecules should be aligned along one
 of the Cartesian axes).
 Contributions from frequencies below 20 1/cm are not included in
 the vibrational sums. Their contributions, if any, are reported separately.


     Temp                                                       Transl     Rotat    Vibrat     Total
     ----                                                       ------     -----    ------     -----

     298.15   Entropy (cal/mole-K):                             34.608    10.415     0.015    45.039
              Internal Energy (Kcal/mole):                       0.889     0.889    13.316    15.094
              Constant Volume Heat Capacity (cal/mole-K):        2.981     2.981     0.092     6.054

              Summary of energy terms
                                                   hartree              eV         kcal/mol           kJ/mol
                                      --------------------     -----------       ----------      -----------
              Bond Energy:              -0.514027806778452        -13.9874          -322.56         -1349.58
              Internal Energy:           0.024053624667862          0.6545            15.09            63.15
              pV/n = RT:                 0.000944186013486          0.0257             0.59             2.48
              Enthalpy H:               -0.489029996097105        -13.3072          -306.87         -1283.95
              -T*S:                     -0.021399475096437         -0.5823           -13.43           -56.18
              Gibbs free energy:        -0.510429471193542        -13.8895          -320.30         -1340.13


     Temp                                                       Transl     Rotat    Vibrat     Total
     ----                                                       ------     -----    ------     -----

     299.14   Entropy (cal/mole-K):                             34.625    10.425     0.015    45.066
              Internal Energy (Kcal/mole):                       0.892     0.892    13.317    15.100
              Constant Volume Heat Capacity (cal/mole-K):        2.981     2.981     0.094     6.055

              Summary of energy terms
                                                   hartree              eV         kcal/mol           kJ/mol
                                      --------------------     -----------       ----------      -----------
              Bond Energy:              -0.514027806778452        -13.9874          -322.56         -1349.58
              Internal Energy:           0.024063177770665          0.6548            15.10            63.18
              pV/n = RT:                 0.000947321474284          0.0258             0.59             2.49
              Enthalpy H:               -0.489017307533503        -13.3068          -306.86         -1283.91
              -T*S:                     -0.021483248259844         -0.5846           -13.48           -56.40
              Gibbs free energy:        -0.510500555793348        -13.8914          -320.34         -1340.32
 

…………

…………



     Temp                                                       Transl     Rotat    Vibrat     Total
     ----                                                       ------     -----    ------     -----

     398.15   Entropy (cal/mole-K):                             36.045    11.278     0.068    47.391
              Internal Energy (Kcal/mole):                       1.187     1.187    13.335    15.709
              Constant Volume Heat Capacity (cal/mole-K):        2.981     2.981     0.299     6.261

              Summary of energy terms
                                                   hartree              eV         kcal/mol           kJ/mol
                                      --------------------     -----------       ----------      -----------
              Bond Energy:              -0.514027806778452        -13.9874          -322.56         -1349.58
              Internal Energy:           0.025033642777425          0.6812            15.71            65.73
              pV/n = RT:                 0.001260867554148          0.0343             0.79             3.31
              Enthalpy H:               -0.487733296446879        -13.2719          -306.06         -1280.54
              -T*S:                     -0.030069226500753         -0.8182           -18.87           -78.95
              Gibbs free energy:        -0.517802522947632        -14.0901          -324.93         -1359.49

其中,

  • 如同输出文件内容所说,这种计算Gibbs自由能的方式,引入了理想气体近似,
  • Moments of Inertia,转动惯量I。转动能级Erotate=h2*J(J+1)/8π2I,其中J为转动量子数也就是能级序号,I为转动惯量(非负整数),h为普朗克常数(h=6.62606896×10-34J·s),π=3.141593。
  • Transl,Rotat,Vibrat,Total三项列出了各个温度时,熵、内能、热容的平移、转动、振动分量与总和。
  • Summary of energy terms,列出了内能、焓、Gibbs自由能等信息。
adf/ir.txt · 最后更改: 2019/12/06 17:00 由 liu.jun

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