# Solid state: force on an ion moved out of position in crystal, involves taylor series

1. Sep 11, 2012

### cjw21

1. The problem statement, all variables and given/known data

2. Relevant equations

All should be there, except taylor series, which is found here:

http://mathworld.wolfram.com/TaylorSeries.html

3. The attempt at a solution

For part a, I got:

F(r)= $\alpha$(ke2)((-r0/r2)+(r0n/rn+1))

since force is the negative derivative of potential.

I'm pretty sure the answer to part b will involve a taylor expansion, but I'm not sure if the f(x) I use will be the equation I found in part a, or the derivative of the equation I found in part a. Additionally, I'm not sure how, in the answer we're supposed to get that's listed in the problem, they got (n-1) and the n term in the second part out of the exponent.

Thanks for any help!

2. Sep 11, 2012

### cjw21

Re: solid state: force on an ion moved out of position in crystal, involves taylor se

sorry, double post