MOPAC Input File Generator

The Input Geometry

Please indicate the relative positions of your atoms in the table below. Note that you don't need to tell which atoms are bonded to which, the theoretical calculations will tell you that.

Choose from H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, and Cl

Calculation Type

Please choose the type of calculation:
Single Point-Fixed Geometry Geometry Optimization Transition State Vibrational Frequencies

Model Hamiltonian

Please choose the model for the calculation:


Please give the charge on your molecule, ion, or complex:


Most molecules and ions have SINGLET lowest energy states. However, molecules and ions with an odd number of electrons have DOUBLET states. Examples of molecules with doublet states include CN, NO, and NO2. A few molecules have two unpaired electrons. Two unpaired electrons give a TRIPLET state. Examples of molecules with TRIPLET states include diatomics B2 and O2. Some atoms have QUARTET lowest energy states. The SINGLET, DOUBLET, TRIPLET, or QUARTET nature of a substance is called its multiplicity.

Please give the multiplicity of your structure:

Output Options

Please choose the type of output you want:
MO Coefficients
Mulliken Bond Orders and Charges
Electrostatic Potential Charges
Hybridization and Sigma-Pi Bond Orders


Type in a descriptive comment to be included in the output.

Copy the output below onto the clipboard and then paste into a Word or SimpleText document. Make sure to include the last blank line; MOPAC expects a final blank line in the input file. Save your Word document as "text only". After running MOPAC, change the file extension of the output file to ".mop". Then you can open this file for 3D-display using your browser and Chime (