What could be causing the error in my AMPAC semi-empirical calculation?

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In summary, the conversation is about an undergraduate student learning about computational chemistry and encountering an error message while using AMPAC semi-empirical methods to model a reaction. The error message is related to reading vibrational frequency data and may be caused by various reasons. The student is seeking clarification on the calculation settings used.
  • #1
rvm
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Hello,

I am an undergraduate student being introduced to the world of computational chemistry. I am modeling a reaction using AMPAC semi-empirical methods, and the output file included an error message. I would appreciate some insight.

The calculation is a chain calculation connecting two structures corresponding to a partial rotation of a molecular rotor. The calculation completed and marked two nodes as potential transition states (node 5 and node 8). Node 5 had two negative vibrations, Node 8 had a single large negative vibration.

My calculation settings:
pm6 rhf singlet fullchn lforce t=auto

Error message:
CconnectionAOut::GetAmpacVibrationData()
Bad Vibration = 8
Line Number 6495

Thank you,

RVM
 
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  • #2
rvm said:
Hello,

I am an undergraduate student being introduced to the world of computational chemistry. I am modeling a reaction using AMPAC semi-empirical methods, and the output file included an error message. I would appreciate some insight.

The calculation is a chain calculation connecting two structures corresponding to a partial rotation of a molecular rotor. The calculation completed and marked two nodes as potential transition states (node 5 and node 8). Node 5 had two negative vibrations, Node 8 had a single large negative vibration.

My calculation settings:
pm6 rhf singlet fullchn lforce t=auto

Error message:
CconnectionAOut::GetAmpacVibrationData()
Bad Vibration = 8
Line Number 6495

Thank you,

RVM

Sorry, but I don't know much about AMPAC. However, I may still be able to help. The error sounds like it is arising from an attempt to read vibrational frequency data from some sort of input or temporary file. This might happen for any number of reasons.

Does the error arise at the beginning of the calculation when the input is read, or sometime later? Also, what do the calculation settings mean? I understand "pm6", "rhf" and "singlet", but what are the other settings?
 

1. What is the AMPAC Semi-Empirical Problem?

The AMPAC Semi-Empirical Problem is a computational chemistry problem that involves using semi-empirical methods to approximate the electronic structure and properties of molecules. It is commonly used in drug design, materials science, and other fields of research.

2. What are semi-empirical methods?

Semi-empirical methods are a type of computational chemistry method that uses a combination of experimental data and theoretical calculations to approximate the electronic structure and properties of molecules. These methods are less computationally intensive than other quantum mechanical methods, making them useful for studying larger molecules.

3. How is the AMPAC Semi-Empirical Problem solved?

The AMPAC Semi-Empirical Problem is typically solved using a software package called AMPAC (Advanced Modeling Program for Atomic and Chemical calculations). This software uses semi-empirical methods such as Austin Model 1 (AM1) or Parametric Method 3 (PM3) to calculate the electronic structure and properties of molecules.

4. What are the limitations of the AMPAC Semi-Empirical Problem?

While semi-empirical methods are useful for studying larger molecules, they are not as accurate as other quantum mechanical methods. This means that the results obtained from the AMPAC Semi-Empirical Problem may not be as precise as those obtained from more advanced methods. Additionally, these methods may not be suitable for studying systems with strong electron correlation or for accurately predicting bond energies.

5. What are some applications of the AMPAC Semi-Empirical Problem?

The AMPAC Semi-Empirical Problem has a wide range of applications, including drug design, materials science, and environmental studies. It is often used to study the electronic structure and properties of large molecules, such as proteins, polymers, and nanoparticles. It can also be used to predict and analyze chemical reactions and to design new molecules with specific properties.

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