Theory: Gradient with respect to particle i
I've been trying to understand a thing which is explained a bit in this answer:
I understand everything up to:
1) I don't understand how he goes from nabla W to W' and an r hat vector.
2) Also I don't understand what is the difference between nabla and ' in this case. I understand nabla is spatial derivative with respect to xyz, while ' might be with respect to q = r/h ?
3) What does the hat vector really mean? Is it just that:
r = (x,y,z) ----> r_hat = (-z,y,x)
But as far as I know a lot of different r_hat can exist in 3d?
I hope someone would take a bit of time explaining this concept to me or maybe guide me to another explenation of how to understand gradient with respect to i computionally.
edited February 19
Why would you not contact the OP (original poster) by placing a comment under his/her answer? They are the best people to explain intentions and notations. I guess that at least for some Stackoverflow community there is the possibility to have an extended conversation in a virtual chatroom as the need be. This does not address your concerns directly, but hopefully helps you find the answer you wish.
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