How do I find the coordinates of the point at which the derivative is 0?

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Rhianne Tallarico 2018-2-20

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https://ww2.mathworks.cn/matlabcentral/answers/383759-how-do-i-find-the-coordinates-of-the-point-at-which-the-derivative-is-0

回答： Walter Roberson 2018-2-20

e=1;
sigma=0.154;
r=linspace(0.154,1,100);
U = @(r) 4*e*((sigma./r).^12)-((sigma./r).^6);
norm_r = r./sigma;
figure
plot(norm_r,U(r))
title('Lennard-Jones Potential')
xlabel('Distance (nm)')
ylabel('Potential Energy')

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Answer 1

Walter Roberson 2018-2-20

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https://ww2.mathworks.cn/matlabcentral/answers/383759-how-do-i-find-the-coordinates-of-the-point-at-which-the-derivative-is-0#answer_306130

在 MATLAB Online 中打开

If you have the Symbolic Toolbox, then

r=linspace(0.154,1,100);
syms R real
location_of_zero_deriv = solve(diff(U(R),R),R);
mask = location_of_zero_deriv >= r(1) & location_of_zero_deriv <= r(end);
location_of_zero_deriv = double( location_of_zero_deriv(mask) );