Real vs complex spherical harmonics for hexagonal symmetry

In summary, the conversation discusses the use of real and complex spherical harmonics for hexagonal symmetry and their association with a finite Lz. The position representation of an eigenvector of Lz is a standard complex spherical harmonic, with a corresponding expression in spherical coordinates. The question of any relation between crystal symmetry and these harmonics is raised, as well as a method for determining their superiority.
  • #1
Junaidjami
2
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TL;DR Summary
Orbital analysis of magnetic anisotropy energy using second order perturbation theory for hexagonal symmetry
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Are real spherical harmonics better than complex spherical harmonics for hexagonal symmetry, which are
directly associated to a finite Lz?
 
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  • #2
An eigenvector of ##L_z## in position representation is a standard complex spherical harmonic, i.e.,
$$\text{Y}_{lm}=P_{lm}[\cos(\vartheta)] \exp(\mathrm{i} m \varphi).$$
Note that in spherical coordinates the position representation of ##\hat{L}_z## reads
$$\hat{L}_z=-\mathrm{i} \hbar \partial_{\varphi}.$$
 
  • #3
vanhees71 said:
An eigenvector of ##L_z## in position representation is a standard complex spherical harmonic, i.e.,
$$\text{Y}_{lm}=P_{lm}[\cos(\vartheta)] \exp(\mathrm{i} m \varphi).$$
Note that in spherical coordinates the position representation of ##\hat{L}_z## reads
$$\hat{L}_z=-\mathrm{i} \hbar \partial_{\varphi}.$$

vanhees71 said:
Is there any relation between the crystal symmetry and real/complex spherical harmonics? And is there a way to judge the superiority of one over the other?
 

1. What is the difference between real and complex spherical harmonics for hexagonal symmetry?

Real and complex spherical harmonics are different mathematical representations of the same physical phenomenon, namely the spatial distribution of a wave on a sphere. Real spherical harmonics are expressed as real-valued functions, while complex spherical harmonics are expressed as complex-valued functions. For hexagonal symmetry, the main difference between the two representations lies in the number of coefficients needed to describe the wave, with complex spherical harmonics requiring fewer coefficients.

2. Which representation is more commonly used in the study of hexagonal symmetry?

In general, complex spherical harmonics are more commonly used in the study of hexagonal symmetry. This is because they require fewer coefficients to describe the wave, making calculations and analysis easier and more efficient. Real spherical harmonics, on the other hand, are often used in specific cases where the wave is purely real.

3. Can real and complex spherical harmonics be used interchangeably for hexagonal symmetry?

While real and complex spherical harmonics are mathematically equivalent, they cannot be used interchangeably in the study of hexagonal symmetry. This is because they represent different physical quantities and have different properties, which can lead to different results and interpretations. It is important to use the appropriate representation depending on the specific problem being studied.

4. How are real and complex spherical harmonics related to each other?

Real and complex spherical harmonics are related through a mathematical transformation known as the complex conjugate. This transformation converts a complex-valued function into its real-valued counterpart, and vice versa. This relationship allows for the conversion between the two representations, but it is important to note that the physical interpretation of the wave may be different in each representation.

5. What are the advantages and disadvantages of using real vs complex spherical harmonics for hexagonal symmetry?

The main advantage of using complex spherical harmonics is their efficiency in representing waves with hexagonal symmetry. They require fewer coefficients and can simplify calculations and analysis. However, the use of complex numbers may be more challenging for some researchers, and the physical interpretation of the wave may be less intuitive. Real spherical harmonics, on the other hand, may be easier to understand and interpret, but they require more coefficients and can be less efficient in certain cases.

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