One final question ... is there a way to extrapolate the curves back to the y-axis?

One final question ... is there a way to extrapolate the curves back to the y-axis?

I am replicating Figure 2 for P3HT.

Download 7904_Medina_2007_ChemMater_Electronics_structure_Charge_transport_polythiophene_chains_Exp_Theoretical_study.pdf
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I appreciate your help!

I am replicating Figure 2 for P3HT.

Download 7904_Medina_2007_ChemMater_Electronics_structure_Charge_transport_polythiophene_chains_Exp_Theoretical_study.pdf
View file details

I appreciate your help!

The plot is a function versus a function with the variable being N for both the y-axis and the x-axis.  N = 8, 12, 16, 20 the x-axis is 1/N and the y-axis are the equations I described before.  The confusing thing here is that the fit using the previously mentioned equations uses N to fit the scatter points.  So it is not a simply display scatter or plot equation issue.  Does this make sense?

The plot is a function versus a function with the variable being N for both the y-axis and the x-axis.  N = 8, 12, 16, 20 the x-axis is 1/N and the y-axis are the equations I described before.  The confusing thing here is that the fit using the previously mentioned equations uses N to fit the scatter points.  So it is not a simply display scatter or plot equation issue.  Does this make sense?

I appreciate your help - since you asked I wanted to show you my whole problem and where the equation I am using comes from.

The problem I am doing is a fit over HOMO/LUMO data obtained from TDDFT.  The equation I using to fit comes from Kuhn and has the form of

E = E_0*sqrt(1+k'/k_0*cos(Pi/(N+1)))

where E_0 is the transition energy, N is the number of double bonds, and k'/k_0 is an adjustable parameter relating he coupling between oscillators and is typically on the order of -0.45.

This equation has been shown to fit over the data (Chem. Mater. Vol. 19, No. 20, 2007, p. 4949).

I was able to fit the HOMO using this expression without difficulty which is the first set of data in the *mws.

The big picture: I am trying to determine the long chain limit for a set of polymers and so using the equation above to fit the data is critical.

My plot problem:

I fit the data using N.  However, the actual plot is performed using E vs. 1/N.

I appreciate your help - since you asked I wanted to show you my whole problem and where the equation I am using comes from.

The problem I am doing is a fit over HOMO/LUMO data obtained from TDDFT.  The equation I using to fit comes from Kuhn and has the form of

E = E_0*sqrt(1+k'/k_0*cos(Pi/(N+1)))

where E_0 is the transition energy, N is the number of double bonds, and k'/k_0 is an adjustable parameter relating he coupling between oscillators and is typically on the order of -0.45.

This equation has been shown to fit over the data (Chem. Mater. Vol. 19, No. 20, 2007, p. 4949).

I was able to fit the HOMO using this expression without difficulty which is the first set of data in the *mws.

The big picture: I am trying to determine the long chain limit for a set of polymers and so using the equation above to fit the data is critical.

My plot problem:

I fit the data using N.  However, the actual plot is performed using E vs. 1/N.