Adjissi Lilia Hi

You can calculate

Free radical energy+ energy of hydrogen- energy of molecule.

Use temperature,bond dissolution energy and other parameters Place them into the equation as unknowns x,y... the outcome must be something say conductivity

Depending on how many variables you have the same number of equations must be placed in the system If x,y only then 2 if x,y,z then 3 and so on express one of the variables through other and keep reducing until you have one left equal to a number in other words Solve as a system of equations for the respectful number of entries 2,3...

Of course to write the equations you must first define what kind of equations they are they cause dependance must not be linear (arithmetic) it can be geometric a^x After that keep simplifying until you have one variable equal to smth Keep records of what you were doing that is Gaussian elimination

I know I made a mess of it :) In the eventuality of you having 2 quadratic or 3 cubic equations etc use a parameter instead of x^2 or x^3 For example m so you wil get smth like:

6m+8y=5

5m+7y=4

solve for m which is 30m +40y=25

30m+42y=24

add second to the first with minus sign

2 y=-1

y=-1/2

30m=45

m=3/2

but since its quadratic x^2=3/2

x=+/-sqr3/2

All the steps for solving system of linear equation are recorded (except of course substitution) and you have Gaussian elimination for the respectful number of entries

Waseem Ahmad Ansari thank you very much Sir I want the calculated by the gaussien logicial according to the equation you have given

Ruslan Pozinkevych thank you Sir so much for this explication of gaus elimination it's so importante to remember the roles. i have locicial gaussien view 5.0 and I would do the calcul by him for calculate the Band dissociation enthalpies (BDE)

Hi Dr Adjissi Lilia . I think it can be calculated as the energy difference between products of dissociation and initial system. So, just detach atoms/fragments, optimize them and then subtract the energy of optimized phenol from the sum of optimized dissociation products. See the link:Article Computation of the bond dissociation enthalpies and free ene...

Aref Wazwaz thank you Sir so much for this explication and for this article, i will read it, thank you verry much.

You are most welcome Adjissi Lilia

Adjissi Lilia you can take a look at this paper, it is very helpful : "Thermochemistry in Gaussian" :

https://gaussian.com/thermo/

Mahdi Achour thank you so much , i will see it