Stable Nuclei present during Homogeneous Nucleation

1. Mar 15, 2010

Hashmeer

1. The problem statement, all variables and given/known data
Assume for the solidification of nickel that nucleation is homogeneous, and the number of stable nuclei is 10^6 nuclei per cubic meter. Calculate the critical radius and the number of stable nuclei that exist at the following degrees of supercooling: 200 K and 300 K.

delta G = 1.27 x 10^-18 (I'm not sure about this value, this could be where I'm going wrong)
n = 10^6
k = 1.38 x 10^-23
T = 319 K (this is also one I'm confused about, is the T value the amount of supercooling or is it the actual temperature, which would be some number under the melting point)
sigma = .255
delta H = -2.53 x 10^9

2. Relevant equations

n = K(1)*exp(- delta G/(k*T))
r^* = \frac{2 \sigma T_m}{\Delta H_s} \frac{1}{\Delta T}
Delta G^* = \frac{16 \pi \sigma ^3 T_m^2}{3\Delta H_s^2} \frac{1}{(\Delta T)^2}

The last 2 equations are from http://en.wikipedia.org/wiki/Nucleation" [Broken] and they are what I used.

3. The attempt at a solution

When I try to solve for K(1) I am getting a ridiculously high number (1.95 x 10^131) which then doesn't fit for the other temperature values because as temperature decreases the number of stable nuclei should decrease, but I was getting the opposite of that.

Thanks for the help.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 4, 2017