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之前用Molclus调用Shermo做构象搜索排序,后面需要详细计算其他的热力学量,因此又单独用Shermo算了一次,但是发现两次计算结果略有偏差,不知道是什么原因,请各位老师指导。
Molclus调用Shermo的设置如下(精简版,完整版请见附件):
Shermo_path= "/sob/Shermo_2.3.5/Shermo" // Command for invoking Shermo
T= 298.15
P= 1.0
sclZPE= 0.9806
ilowfreq= 2
计算完成后通过isostat排序,第二的构象能量最低,从isomers.xyz文件中读取到“ G = -1317.609596 Gcorr = 0.184924 a.u. Nimag = 0 Frame: 2 Step: 2 Geom: 2”。
但是后面用单独用Shermo计算的结果和上面G以及Gcorr都有偏差。
从ORCA计算结果中读取到Final Single Point Energy=-1317.79451960089 a.u.,粘贴到Shermo的settings.ini文件中,为了保证一致性,使用了未更新的Shermo 2.3.5版本,设置如下(精简版,完整版请见附件):
E= -1317.79451960089 //Electronic energy in a.u. If E= 0, then it will be loaded from input file
T= 298.15 //in K. By specifying lower, upper limits and stepsize, e.g. 50,200,10, it can be scanned
P= 1.0 //in atm. By specifying lower, upper limits and stepsize, e.g. 0.5,20,0.1, it can be scanned
sclZPE= 0.9806 //Frequency scale factor for ZPE
ilowfreq= 2 //Treatment of low frequencies. 0: Harmonic (RRHO). 1: Raising low frequencies (Truhlar). 2: Entropy interpolation (Grimme). 3: Entropy and internal energy interpolations (Minenkov)
这些输入都保持了和Molclus调用Shermo的设置相同。
Shermo计算输出的结果如下(精简版,完整版请见附件):
===========================
========== Total ==========
===========================
Total q(V=0): 2.645657E+046
Total q(bot): 7.735314E-063
Total q(V=0)/NA: 4.393216E+022
Total q(bot)/NA: 1.284479E-086
Total CV: 312.575 J/mol/K 74.707 cal/mol/K
Total CP: 320.890 J/mol/K 76.694 cal/mol/K
Total S: 602.645 J/mol/K 144.036 cal/mol/K -TS: -42.944 kcal/mol
Zero point energy (ZPE): 607.496 kJ/mol 145.195 kcal/mol 0.231383 a.u.
Thermal correction to U: 662.470 kJ/mol 158.334 kcal/mol 0.252322 a.u.
Thermal correction to H: 664.949 kJ/mol 158.927 kcal/mol 0.253266 a.u.
Thermal correction to G: 485.271 kJ/mol 115.982 kcal/mol 0.184830 a.u.
Electronic energy: -1317.7945196 a.u.
Sum of electronic energy and ZPE, namely U/H/G at 0 K: -1317.5631368 a.u.
Sum of electronic energy and thermal correction to U: -1317.5421980 a.u.
Sum of electronic energy and thermal correction to H: -1317.5412539 a.u.
Sum of electronic energy and thermal correction to G: -1317.6096898 a.u.
可见 Thermal correction to G: 0.184830 a.u.与前面的Gcorr = 0.184924 a.u. 有偏差, Sum of electronic energy and thermal correction to G: -1317.6096898 a.u.与前面的G = -1317.609596也有偏差。
请问各位老师,这种偏差是如何造成的?
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