Position Vector in Wave Functions

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SUMMARY

The discussion focuses on creating a 2-D electron energy density plot in Mathematica using the superposition of symmetric and anti-symmetric wave functions. The wave functions are defined as $$\Psi_s(\textbf{r})$$ and $$\Psi_a(\textbf{r})$$, with specific k-values derived from the equation $$\textbf{k}_i=\frac{4\pi}{3d_b}$$. The user seeks clarification on the appropriate position vector $$\textbf{r}$$ to input into Mathematica, questioning whether to use $$\hat{x}$$, $$\hat{y}$$, or a combination of both. The discussion emphasizes the need to correctly represent the position vector and the dot product in Mathematica for accurate plotting.

PREREQUISITES
  • Understanding of wave functions in quantum mechanics
  • Familiarity with Mathematica for plotting and vector operations
  • Knowledge of 2-D coordinate systems and position vectors
  • Basic grasp of trigonometric functions and their applications in physics
NEXT STEPS
  • Learn how to implement vector operations in Mathematica
  • Study the principles of quantum mechanics related to wave functions
  • Explore Mathematica's plotting functions for 2-D visualizations
  • Investigate the mathematical representation of dot products in vector calculus
USEFUL FOR

Students and researchers in physics, particularly those working with quantum mechanics and computational modeling using Mathematica. This discussion is beneficial for anyone looking to visualize wave functions and energy density plots effectively.

Rosie135
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Hello,
I need to create a 2-D electron energy density plot in Mathematica to compare with my STM experimental results in my lab class. This would be done by plotting the superposition of the symmetric and anti-symmetric wave functions,

$$\Psi_s(\textbf{r}) = \sum_{i=1}^{3}a_icos(\textbf{k}_i\cdot\textbf{r})$$
$$\Psi_a(\textbf{r}) = \sum_{i=1}^{3}b_isin(\textbf{k}_i\cdot\textbf{r})$$
and squaring it to get this,
$$\Psi_s^2(\textbf{r})+\Psi_a^2(\textbf{r})=\Big[\sum_{i=1}^{3}a_icos(\textbf{k}_i\cdot\textbf{r})\Big]^2+\Big[\sum_{i=1}^{3}b_isin(\textbf{k}_i\cdot\textbf{r})\Big]^2$$
Where the k's are equal to,
$$\textbf{k}_1=\frac{4\pi}{3d_b}\hat{y}$$
$$\textbf{k}_2=\frac{4\pi}{3d_b}(-\frac{1}{2}\sqrt{3}\hat{x}-\frac{1}{2}\hat{y})$$
$$\textbf{k}_3=\frac{4\pi}{3d_b}(\frac{1}{2}\sqrt{3}\hat{x}-\frac{1}{2}\hat{y})$$
Although this seems trivial, my question is what do I set position vector r to when I am inputting to Mathematica? Could I just set it to $$\hat{x}$$ or $$\hat{y}$$ or even $$\hat{x}+\hat{y}$$
And also, since the dot product of the argument Sin and Cos would contain a scalar, I would need to attach a variable to that in order to plot it right? Would that just be variables x and y? The result should just be a uniform distribution of "bright spots" but my results have been way off. My inputs to Mathematica may be wrong, but before I start figuring out where I went wrong in Mathematica, I want to make sure my concept of how to represent these quantities is correct.
 
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I'd work with the components of the vectors and express them as lists. Mathematica has pretty intuitive operations with vectors and vector calculus. So for any vector ##\vec{v}##, you map
$$\vec{v}=v_x \hat{x} + v_y \hat{y} \mapsto \{v_x,v_y \}$$
in Mathematica. The dot product is then just written as {a,b}.{c,d}=ac+bd in Mathematica.
 
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vanhees71 said:
I'd work with the components of the vectors and express them as lists. Mathematica has pretty intuitive operations with vectors and vector calculus. So for any vector ##\vec{v}##, you map
$$\vec{v}=v_x \hat{x} + v_y \hat{y} \mapsto \{v_x,v_y \}$$
in Mathematica. The dot product is then just written as {a,b}.{c,d}=ac+bd in Mathematica.

Thank you, that makes much more sense!
 

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