# Homework Help: Solid State Physics-simple question on lattice vacancies

1. May 3, 2009

### trv

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

If silver melts at 9620C and contains an intrinsic relative concentration of 3*10^(-7) lattice vacancies, estimate the energy required to remove an atom from the interior of the crystal lattice.

2. Relevant equations

The above is a past exam question and the equation wasn't given but I'm pretty sure, the following, which gives the number of vacancies n in thermal equilibrium is the relevant one.

$\frac{n}{N}=exp (\frac{-E_v}{k_BT})$

3. The attempt at a solution

It probably simply is a matter of plugging into the above equation, with n/N=3*10^(-7),
Ev being what we need.

The T is what I'm a little confused about if it was a temperature other then the melting point, I'd be happy to just plug it in. At the melting point however, there is no crystal and hence the question of vacancies doesn't arise.

Or is it simply that the crystal is at the melting point without actually having melted?