Non integer power doesn't work

I am solving a nonlinear problem. I need to use some exponential term in my energy function but I see that whenever the power is not an integer it immediately creates nan and diverge. For example:

    • C **1. → works
    • C 1.0000001-> doesn’t work with:
      Newton iteration 1: r (abs) = -nan (tol = 1.000e-06) r (rel) = -nan (tol = 1.000e-06)

Does anybody know what is the solution?

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Thanks for your advice. But if you see my question it has nothing to do with those guidlines.
As I mentioned the problem works with power=1. but doesn’t work with power=1.0000001

Did you solve your problem by any chance?