Determination of time-dependent coefficients (QM)

In summary, the conversation discussed finding the time-dependent coefficients for the equation \Psi(r,t) = \sum_n C_n(t) e^{-i E_n t} \psi(r) in order to model the system of benzene. The speaker mentioned using Hückel's method to determine the time-independent solution, but was struggling with transitioning to time-dependent coefficients. There was also mention of an error in the electron density and the need to solve for the coefficients using orthonormal vectors.
  • #1
Aeon
21
0
Hi,

I am trying to solve the following equation:

[itex]\Psi(r,t) = \sum_n C_n(t) e^{-i E_n t} \psi(r)[/itex]

to find the [itex]C_n(t)[/itex]s.

The system I am modeling is benzene. I can, by Hückel's method, determine the time-independent solution. The apparently obvious transition from time-independent coefficients to time-dependent coefficients is troubling me. A simple plot of the squared coefficients indicates that my electron density vanishes, which is indicative of error.

I'm wondering how is the proper way to solve for the time-dependent coefficients...
 
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  • #2
Did you leave off a subscript? If you meant to write ψ(r,t) = ∑ Cn(t) exp(-iEnt) ψn(r) where the ψn(r)'s are orthonormal, then
∫ψ(r,t) ψn(r) dr = Cn(t) exp(-iEnt), which gives you Cn.
 
  • #3
I forgot a subscript, you are right.

Also, the problem was that my vectors were not orthogonalized. Thanks!
 

Related to Determination of time-dependent coefficients (QM)

1. What is the purpose of determining time-dependent coefficients in quantum mechanics?

The determination of time-dependent coefficients in quantum mechanics is necessary for understanding the behavior and evolution of quantum systems over time. These coefficients describe the time-dependent probability amplitudes for different states of a system, allowing us to make predictions about its behavior and interactions with other systems.

2. How are time-dependent coefficients calculated in quantum mechanics?

Time-dependent coefficients are typically calculated using the Schrödinger equation, which describes the time evolution of a quantum system. This equation takes into account the Hamiltonian of the system, as well as any external forces or potential energies that may act upon it.

3. What factors can affect the time-dependent coefficients in quantum mechanics?

In addition to the initial state of a quantum system, the time-dependent coefficients can be influenced by external forces, potential energies, and interactions with other systems. These coefficients can also be affected by the presence of measurement or observation, as described by the concept of quantum decoherence.

4. Can time-dependent coefficients change over time in quantum mechanics?

Yes, time-dependent coefficients can change over time in quantum mechanics. This is because the evolution of a quantum system is described by the Schrödinger equation, which takes into account the time-dependent behavior of the system's Hamiltonian and external forces. As these factors change, the time-dependent coefficients will also change.

5. What are some applications of determining time-dependent coefficients in quantum mechanics?

The determination of time-dependent coefficients in quantum mechanics has many practical applications, such as in the development of quantum computing and quantum communication technologies. It is also important in understanding the behavior of complex quantum systems, such as atoms and molecules, and in studying the dynamics of chemical reactions at the quantum level.

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