Morse potential constants using matlab

V(r)=D[exp(−2a(r−ro))−2exp(−a(r−ro))]: This is the mores potential equation. I have the data V(r) and r, how can I find the constant D, a, ro using matlab? I really don’t know how to start. Could you give me some advices?

[Jiri Hajek]

Hi, this is a nonlinear regression problem, which is solvable using optimization methods. Depending on whether you need to automate the task by using programmatic solution, whether you need to use MATLAB to achieve this, whether you have access to optimization toolbox and what is the size of your data, it is surely solvable in MATLAB, but Excel may give you a solution as well...

Answer 1

[Luca Ferro]

try this:

syms D a ro ; %create symbolic scalar variables

eq = V==D*(exp(-2*a*(r-ro))-2*exp(-a*(r-ro))); %create equation

sol=solve(eq); %solve the equation

since you have 1 equation and 3 variables the output will be symbolic (assuming V and r are scalars)

EDIT:

as Walter Robertson highlighted in the comments, it's better to specify what to solve for:

sol=solve(eq, [ro a D]); %solve the equation

[Walter Roberson]

You should tell solve which variable you want to solve for

[Walter Roberson]

One equation cannot be solved for three variables.

When you do not specify which variable to solve for, MATLAB uses symvar to figure out which free variables exist in the equation(s). It has a priority order that starts with x y z. After prioritizing it uses the first on the list, as many as there are equations.

[Luca Ferro]

Specifying all of three at least returns a struct with values for all of them.

With only one you get the symbolic solution, that's why i left it without specification in first place.

I don't know what the OP is looking for, so i gave him some alternatives after you pointed out the inaccuracy of my reply.