Hello,
I already finished my work
@ nyxynyx : Do you want to know that, or do you try to help me? Because everything is finished already. I don't need any replies to this thread, but thanks.
Mr. Fogg
Okay, thanks.
I found an article, where the author says:
J_{i,j} is a symmetric matrix containing the exchange parameters between spins at sites i and j.
How does the spin vector operator look like, for Ions with spin e.g. 3/2 or 5/2 ?
Regards,
Phileas
Thanks peteratcam,
I used the wrong expansion before, so I've the correct result now.
How can J look like in this case? I think, it must be a 4x4 Matrix, right?
Is the product of matrix J and the spin-spin-coupling matrix (I call it A) a tensor product, or just a normal matrix multiplication...
Okay, I see. So from the Second Law, we get for the Gibbs Free Energy d(U+pV -TS) < 0 \Rightarrow dU +pdV - TdS < 0 .
And to deal with the change in entropy, we take the Clausius (In)equation dS = \frac{\delta Q}{T}
The system prefers the state with lower Gibbs Free Energy. So I have to...
Thanks,
I understand now, one could explain it by taking a look at the p-T diagram.
\lim_{T \to 0} \left( \frac{\partial p}{\partial T} \right)_V = 0
The coexistence curve starts at zero p and T and the fusion curve goes to infinity. So there must be a temperature in between, where a...
Thanks DrDu,
Since in equilibrium the Gibbs' Free Energy is a minimum, the system should prefer the lower chemical potential. So this should be correct, to gain energy from lower to higher potential.
Mr.Fogg
Hello,
right now, I am learning thermodynamics with Reichl: "A modern Course in Statistical Physics"
In chapter 3.C page 100 "classification of phase transitions", the text says:
"As we change the independent intensive variables (p, T, x_1,... ,x_l) of a system,
we reach values of the...
:biggrin: :biggrin: :biggrin:
Now I found my mistake.
I didn't replace the dot with a comma in the file, I got. That's why there occurred these incredible angles :smile:
Now I will revise my analysis and keep your help in mind. When a question occurs, I will ask you again.
Thank You...
The new wave vector in our experiment is final minus initial wave-vector:
\vec{q} = \vec{k}_f - \vec{k}_i
and it's z-component is
q_z = 2 k \sin(\alpha_i)
One measured peak is for example at 2 \Theta = 157523,511 °. In my calculation
1) Division by 2 gives \Theta = 78761,756 °
2) Converting into radiants (for OpenOffice Calc) gives \Theta = 1374,652
3) now calculating (with OpenOffice Calc) \sin(\Theta) = -0,979
So I get a negative...
Thank You,
where can I get the JCPDS file?
When I convert the measured angle 2 \Theta into the z-component of the wave vector with
q_{z,i} = \frac{4 \pi}{\lambda} \sin(\alpha_i)
do I have to halve 2 \Theta ?
Mr. Fogg
Hello,
thanks!
Do I also have to convert 2 \Theta into Radians when I use the Bragg's Law? In my calculation, I sometimes get a negative d , is that possible?
How do I Index the peaks with Miller Indices?
I don't know, how this equation helps me
\frac{1}{d_{hkl}^2} = \frac{4}{3}...
Hello,
I have X-Ray Diffraction Data: Intensity versus angle 2 \Theta and shall find out the lattice constant and even better the crystal structure. The Data is from a \Theta-\ThetaDiffractometer. \lambda = 1,54 \cdot 10^{-10}m
I know that I have to find the peaks and can calculate d from...