Hello everyone. I'm having trouble determining an intermediate point between conformers a and b that I show in Fig. 1. Figure 1. This reaction involves the ...
Hello everyone. I'm having trouble determining an intermediate point between conformers a and b that I show in Fig. 1.
Figure 1 This reaction involves the rotation of the dihedral (torsional) angle α (Figure 1). Possibly at said intermediate point α≈90 ° and with this model assumption such an intermediate point which I show in Figure 2.
Figure 2: TS Guess En Route Section I write:: # opt=(calcfc,ts,noeigentest) freq rb3lyp/6-311g(d,p) geom=connectivity And I execute the calculation. Obtaining the structure shown in Figure 3.
Figure 3: Flat molecule Could you tell me how I should approach this problem, it would be very helpful if you send me the .gjf input file indicating which method I should use with the appropriate Route Section. I enclose the .gjf input files with the Cartesian coordinates of the geometries optimized at the rb3lyp / 6311g (d, p) level of both conformers, and the TS guess. An additional question is regarding the calculation of enthalpy, entropy, free energy, etc. The calculation of these values implies the total energy which is the sum of the electronic energy plus the energy at the zero point (ZPVE) (Equation 1) total electronic (1) 𝐸0K = 𝐸DFT + ZPVE
But the ZPVE value must be multiplied (scaled) by appropriate values that the literature reports (scale factor), this in order to eliminate systematic errors. At this point I have the question: How should I proceed, should I multiply by a scale factor to obtain more accurate thermodynamic data? or simply do not scale by any value. The Gaussian website also indicates how to perform calculations of this type: http://gaussian.com/thermo/ But it does not indicate whether it should scale to ZPVE. Thanks for your attention.
