目录

DFT计算溶剂化自由能(Free Energy of Solvation)

基本理论

溶剂化自由能涉及到三个概念:

三项能量的加和得到了溶剂化自由能(free energy of solvation)。本文以乙醇的水溶液为例说明。

从理论上来讲,这种溶剂化自由能定义无法考虑温度因素,因此在计算溶剂中的化学反应的时候,并不使用这种方法。

参数设置

溶剂化模型使用COSMO:

结果查看

计算完毕之后,点击SCM LOGO > Output > Properties > Bonding Energy Decomposition:

                                                   hartree              eV         kcal/mol           kJ/mol
                                      --------------------     -----------       ----------      -----------

Pauli Repulsion
  Kinetic (Delta T^0):                  14.497580325209100        394.4992          9097.37         38063.39
  Delta V^Pauli Coulomb:                -7.494397827228694       -203.9329         -4702.81        -19676.54
  Delta V^Pauli LDA-XC:                 -1.901989307460891        -51.7558         -1193.52         -4993.67
  Delta V^Pauli GGA-Exchange:            0.075557318257111          2.0560            47.41           198.38
  Delta V^Pauli GGA-Correlation:        -0.025815888798236         -0.7025           -16.20           -67.78
                                      --------------------     -----------       ----------      -----------
  Total Pauli Repulsion:                 5.150934619978390        140.1641          3232.26         13523.78
 (Total Pauli Repulsion =
  Delta E^Pauli in BB paper)

Steric Interaction
  Pauli Repulsion (Delta E^Pauli):       5.150934619978390        140.1641          3232.26         13523.78
  Electrostatic Interaction:            -1.027662205887210        -27.9641          -644.87         -2698.13
 (Electrostatic Interaction =
  Delta V_elstat in the BB paper)
                                      --------------------     -----------       ----------      -----------
  Total Steric Interaction:              4.123272414091180        112.2000          2587.39         10825.65
 (Total Steric Interaction =
  Delta E^0 in the BB paper)

Orbital Interactions
  A:                                    -5.878082223362767       -159.9508         -3688.55        -15432.90
                                      --------------------     -----------       ----------      -----------
  Total Orbital Interactions:           -5.878082223362765       -159.9508         -3688.55        -15432.90

Alternative Decomposition Orb.Int.
  Kinetic:                             -12.874835352590662       -350.3421         -8079.08        -33802.88
  Coulomb:                               6.744367507777624        183.5236          4232.15         17707.33
  XC:                                    0.252385621450268          6.8678           158.37           662.64
                                      --------------------     -----------       ----------      -----------
  Total Orbital Interactions:           -5.878082223362770       -159.9508         -3688.55        -15432.90

  Residu (E=Steric+OrbInt+Res):         -0.000001286513520          0.0000             0.00             0.00


  Solvation Energy (el):                -0.009421636565212         -0.2564            -5.91           -24.74

Post-SCF Solvation Energies
  Solvation Energy (cd):                 0.000954860965897          0.0260             0.60             2.51

Total Bonding Energy:                   -1.763277871384419        -47.9812         -1106.47         -4629.49

其中Solvation Energy (el)表示electrostatic energy,Solvation Energy (cd)表示cavity formation Energydispersion repulsion Energy。这里,二者el、cd分别为-5.91 kcal/mol、0.60 kcal/mol。

三项之和,即为溶剂化自由能(Free Energy of Solvation)。

另有一种使用COSMO-RS方法计算溶剂化Gibbs自由能的方式,参考:COSMO-RS计算溶剂化自由能