We consider here
the relationship between 33
3
3
First we start with only the angular parts. For
these are
the spherical harmonics
These are complex.
Note that the dependence is the same; it depends only on l and the absolute value of m.
We can plot the squares of the magnitudes as a function of
and
and colour them according to the
phase. Red means a phase of zero (positive real number) and cyan means a phase of
(negative
real number). The phase runs in opposite directions for these two spherical harmonics. The
z axis is pointing up and towards the
viewer, the x axis
is pointing forward and to the left and the y axis is back and to the right.
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Y1,1 or p1 | Y1,-1 or p-1 |
If we take linear combinations of these we get the more usual real px and py angular functions:
and
. We can plot them in the same way, plotting their squares as a
function of
and
. Again red means a phase of zero (positive real number) and cyan means a phase of
(negative real number).
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px | py |
These functions
have angular nodes at certain values. cos(
) is zero for
in the opposite directions of 90 and
270 degrees, giving a single vertical nodal plane that includes the y and z
axes. Likewise sin(
) is zero at 0 and 180 degrees giving a vertical nodal plane that
includes the x and
z axes. Notice that if we were working
with, say, m=3
and m=-3,
the phase would show three repeated colour sequences in a full turn, we would get cos(3
) and
sin(3
), and there would be three vertical nodal planes.
So far we have
only plotted angular functions, but now we focus on the 3 hydrogen orbital, which is the
product of the angular function above and a radial function, which is given in atomic units
as
(To convert to SI
units, divide every r by a0
and multiply the expression by .) So there is a radial node at r = 6. If we put both the radial and angular
parts together we get the complete function
The subscripts of
the orbitals (x, x2-y2 etc.) are found by converting the spherical coordinates back to cartesian coordinate.
Here we see that rsin()cos(
) is x, so
we can write it as
Note that we get rid of all the angles but we are allowed to leave rs in the expression. We can make a contour plot of a section of the wavefunction through the x-y plane. The radial node is the blue circle. The y axis is an angular node (plane in 3-D).
The usual plot is a 3-D plot of a contour of the wavefunction enclosing a certain probability. The 90% contour for the 3px orbital is at a wavefunction value of 0.00303 in atomic units (it is non-trivial to calculate this number).
We can see the inner lobes a bit more clearly if we look at a contour that encloses less probability.