Plotting
the distribution of the tilt angle cosines (figure 12 b) shows that
the chromophore is hydrophobic, and the weakly preferred average tilt
angle is about 74^{o} to the surface normal. Calculating the
order parameters for each frame, and averaging over the whole 10 ns
simulation gives 〈P_{1}〉=0.237 and 〈P_{3}〉 = -0.084.
The D parameter calculated through SHG can be expressed in
terms of the Legendre polynomials of Θ_{tilt}:
D = (2〈P_{3}〉+3〈P_{1}〉) / 5〈P_{1}〉
Evaluating
this equation for the 10 ns simulation resulted in a value of D
= 0.458. This differs from the experimental value, which is close to
the weak limit^{33}
an alternative way to view this is to consider the value of <P_{3}>,
which tends to zero in the weak limit.
Figure 12. The normalised distributions of the tilt angles, left hand
plot, and the cosines of the tilt andles, over the simlation for each
chromophore. |