# Possible typo in Ashcroft & Mermin's book?

1. Sep 17, 2008

### FranzDiCoccio

Hi,

I was taking a look to Appendix M of A&M "Solid State Physics" (Conservation of Crystal Momentum). Seems to me that in Eq. (M.6), at page 785 in my edition, the symbol Pi (capital P, defined for the ions) is used in place of pi (small p, defined for additional particles).

I'm new to the forum, so I'm not sure that this kind of comment fits in this topic or rather in Homework and Coursework...

I also hope I'm not taking a blunder, and that this comment is not too useless.

Cheers

Last edited: Sep 17, 2008
2. Sep 17, 2008

### olgranpappy

I think you are correct--it's a typo.

In fact, A+M don't use the symbol $${\bf P}_i$$ for the ions, or anywhere else in the appendix. They use $${\bf P}({\bf R})$$. Thus it seems even more reasonable that what we they have is a typo.

3. Sep 18, 2008

### FranzDiCoccio

Yes, sorry, I meant P(R) instead of Pi. Seems I introduced a typo as well.
Anyway, the point is that (Eq. M6) should feature a small p instead of a capital P.

Thanks a lot for replying. Probably not a very dangerous typo, but I thought it was perhaps worth sharing.

Cheers

F

4. Sep 25, 2008

### FranzDiCoccio

I think I've spotted another typo. It's in problem 5 of Chapter 17 "beyond the independent ..." (page 352 in my edition of the book).
Problem 5 illustrates the derivation of equation (17.56), i.e. $$\chi(q)$$ in the Lindhard theory of screening. I think $$\psi_k(r)^2$$ should be $$|\psi_k(r)|^2$$ in equation (17.80).

Hope someone finds this useful.

cheers