Input Requirements

To successfully run easyPARM, the following input files are required:

1. Hessian Matrix Files

The Hessian matrix is essential for force field parameter derivation. It can be provided in one of the following formats:

• Checkpoint File (.chk): Contains the Hessian matrix from a Gaussian frequency calculation.
• Formatted Checkpoint File (.fchk): Similar to .chk, but in a human-readable format.

• Gaussian Output File (.log): Contains the Hessian matrix from a single-point frequency calculation. Ensure the input file includes the keyword:

  iop(7/33=1)
  

• Orca Output File (.hess): Stores the Hessian matrix from a single-point frequency calculation performed in Orca.
• GAMESS Output File (.dat): Stores the Hessian matrix from a single-point frequency calculation performed in GAMESS.

2. Optimized Molecular Structure

• XYZ Format (.xyz): This file contains the optimized molecular geometry of the system.

3. Charge Output Files

Charge output files contain electrostatic potential (ESP) charge distributions. Supported formats include:

• Gaussian Charge Output
  • RESP Charges (.log)
• Orca Charge Output
  • CHELPG Charges (.out)
  • RESP Charges (.vpot)
• GAMESS Charge Output
  • RESP Charges (.dat)
  • GAMESS Charges (.log)

These input files ensure smooth operation of easyPARM and accurate force field parameter derivation.

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