- #1
Asteropaeus
- 143
- 36
As part of physical chemistry I am reading up group theory for molecular symmetries.
I realize the way chemistry textbooks treat this must be very different from what mathematicians do.
So I want to know how I take a point group, find the matrix operations and get the character table.For an C2 rotation, in terms of coordniates, x changes into -x, y into -y and z stays the same.
\begin{array}{ccc}
-1 & 0 & 0 \\
0 & -1 & 0 \\
0 & 0 & 1 \end{array}
But my textbook has an example where they have something similar to d-orbitals, with lobes of different electron densities, on a molecule. It expresses everything not in terms of coordinates, but objects. So d orbitals change sign when the directions the lobes point into change. And the two d orbitals not on the central atom switch.
So it gives the matrix like this
\begin{array}{ccc}
-1 & 0 & 0 \\
0 & 0 & -1 \\
0 & -1 & 0 \end{array}
And that operating on (Ps, Pa, Pb) gives (-Ps, -Pa, -Pb) where Ps is central, Pa and Pb are terminal. It seems it only talks about the positive lobe of that p orbital.
And then later introduce the same character table for C2v.
It is so confusing what the basis is, and how to find an irreducible representation.
Especially so when the character table doesn't talk about x, y, z but about abstract rotations and d orbitals, apparently a certain way in which two axes are mixed.
All youtube videos I checked, the lecturer explains this stuff and then says, "You don't need to think about what, A1, A2, B1, E and the basis are or what is really happening. You just learn to do this operation, then later on you will find it very useful."
Something is wrong in my understanding, and I can't figure out where it is. I keep going in loops. I am stumped. I don't even know if I asked the correct question.
I realize the way chemistry textbooks treat this must be very different from what mathematicians do.
So I want to know how I take a point group, find the matrix operations and get the character table.For an C2 rotation, in terms of coordniates, x changes into -x, y into -y and z stays the same.
\begin{array}{ccc}
-1 & 0 & 0 \\
0 & -1 & 0 \\
0 & 0 & 1 \end{array}
But my textbook has an example where they have something similar to d-orbitals, with lobes of different electron densities, on a molecule. It expresses everything not in terms of coordinates, but objects. So d orbitals change sign when the directions the lobes point into change. And the two d orbitals not on the central atom switch.
So it gives the matrix like this
\begin{array}{ccc}
-1 & 0 & 0 \\
0 & 0 & -1 \\
0 & -1 & 0 \end{array}
And that operating on (Ps, Pa, Pb) gives (-Ps, -Pa, -Pb) where Ps is central, Pa and Pb are terminal. It seems it only talks about the positive lobe of that p orbital.
And then later introduce the same character table for C2v.
It is so confusing what the basis is, and how to find an irreducible representation.
Especially so when the character table doesn't talk about x, y, z but about abstract rotations and d orbitals, apparently a certain way in which two axes are mixed.
All youtube videos I checked, the lecturer explains this stuff and then says, "You don't need to think about what, A1, A2, B1, E and the basis are or what is really happening. You just learn to do this operation, then later on you will find it very useful."
Something is wrong in my understanding, and I can't figure out where it is. I keep going in loops. I am stumped. I don't even know if I asked the correct question.