How Can You Determine the Wavefunction ψ(r) from Electron Density |\psi(r)|^2?

In summary, the conversation discusses the difficulty in finding the corresponding wave function (ψ(r)) from a given probability density (|\psi(r)|2). The use of a Fourier transform is suggested, but it is mentioned that this may not always be possible due to the fact that multiple wave functions can lead to the same probability density. It is also mentioned that if the wave function is nondegenerate and has no spin or angular dependence, it can be simplified to a real function by taking the square root.
  • #1
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I have a 3 dimensional orbital-specfic electron density function ( |[itex]\psi[/itex](r)|2 ) for all relevant r values. How would I go about finding the corresponding [itex]\psi[/itex](r)? I know it would be something related to a Fourier transform, I'm just unsure about how to go about performing it in mathematica or matlab. Can anyone give me any pointers?
 
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  • #2
You can't. Probability density carries less information than wave function. Many wave functions may lead to the same probability density. Even Fourier can't help.
 
  • #3
If it's as simple as you're making it sound, with no spin dependence or (θ,φ) dependence, just r dependence, then the wavefunction ψ for a nondegenerate stationary state can always be chosen to be real. (Proof: by time-reversal invariance ψ* is also a solution, so if there's only one solution then ψ = ψ*.) So if that's the case, just take the square root.
 

FAQ: How Can You Determine the Wavefunction ψ(r) from Electron Density |\psi(r)|^2?

What is "Psi" in terms of probability density?

Psi, also known as the wave function, is a mathematical function that describes the probability amplitude of a quantum system. It represents the state of a system at a given time and is used to calculate the probability of obtaining a certain measurement from that system.

How is "Psi" related to probability density?

Psi is directly related to probability density through the Born rule, which states that the probability of obtaining a certain measurement from a quantum system is equal to the square of the absolute value of the wave function at that point in space and time.

Can "Psi" be negative or complex?

Yes, Psi can take on negative or complex values. This is because it is a mathematical function and can have both real and imaginary components. However, when calculating probability, Psi is squared, so the negative or complex values are eliminated.

How is "Psi" used in quantum mechanics?

"Psi" is a fundamental concept in quantum mechanics and is used to describe the state of a quantum system. It is used to calculate the probability of obtaining a certain measurement from the system and to describe the evolution of the system over time.

Can "Psi" change over time?

Yes, "Psi" can change over time. This is known as wave function collapse, where the state of a quantum system is determined by a measurement, causing the wave function to "collapse" to a particular value. The change in "Psi" over time is described by the Schrödinger equation.

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