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 arrhenius plot : user-defined function

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T O P I C    R E V I E W
jwoh Posted - 09/03/2020 : 12:01:23 AM
Hi everyone.

I got the data for the integrated photoluminescence intensity as a function of temperature.
To find the activation energy, I changed the x-axis to 1000/T and the y-axis to ln(y) and then fitted the Arrhenius equation with a user-defined function.

However, the message 'Fit did not converge-reason unknown' continuously appear.

The functions, variables, and parameters I used are as follows.

Independent Variables: T
Dependent Variables: I
Parameter Names: A, E
Function Form: Origin C
Function:
I=I0/(1+A*exp(-E/kT))
Constants:
I0= integrated PL intensity at 0K
k=1.38*10^(-23); boltzmanm constant

Please let me know what needs to be corrected or supplemented.
In addition, please inform me of Parameter Initialization.

Thank you.
5   L A T E S T    R E P L I E S    (Newest First)
Huda.S Posted - 04/08/2022 : 2:07:56 PM
Hi Chao

I try it, it is work

thank you too much
ChaoC Posted - 04/06/2022 : 09:03:08 AM
Hi Huda.S,

If you go to Tools>Fitting Function Builder you can define k as a constant in the Variables and Parameters section. Then, on the next page you can switch to the Constants tab and define Boltzmann's constant.

Chao
Huda.S Posted - 04/06/2022 : 08:09:32 AM
Hello

I followed the previous steps but there is a place for the constants and I put k (Boltzmann's constant) but it didn't ask to define the value for it
Is this considered to be predefined in the program by the value of the constant 8.6*10^-5 ev/k-1
jwoh Posted - 09/03/2020 : 07:04:27 AM
Hi Shirley.

With your advice, the fitting was successful.

Thank you.

Shirley_GZ Posted - 09/03/2020 : 03:00:52 AM
Hi Jwoh,

The function body should be defined as below:


And, the initial value for parameter E should have similar magnitude with the parameter k, such as 1E-22

Please correct the function and try to do the fitting again.

Thanks,
Shirley

Originlab Technical Service Team

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