I am trying to calculate geometry optimization of cyclodextrin, however, the computer always show error 2070 in gaussian. I used sem-empirical pm3 and try pm6, and tried to find any method to do this work, but every try could not work. I hope any body on Jiskha can give me instruction. I really appreciate.
Error 2070 in Gaussian typically indicates an issue with the geometry optimization of a molecule. Here are a few possible reasons for the error and some steps you can take to resolve it:
1. Insufficient memory: This error can occur if the calculation requires more memory than is available. You can try increasing the amount of memory allocated for the calculation. This can be done by adding the `%Mem` line in your Gaussian input file and specifying a larger memory value, such as `%Mem=XXGB`, where "XX" represents the amount of memory you want to allocate.
2. Convergence issues: If your molecule has complex or flexible geometry, it may require a more sophisticated optimization method to converge. You can try using a different optimization algorithm, such as the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method, which is often more effective for difficult optimizations. This can be specified by adding the `Opt=Method` keyword in your Gaussian input file, where "Method" represents the optimization algorithm (e.g., Opt=BFGS).
3. Incompatible method or basis set: The error could be due to using an inappropriate method or basis set for cyclodextrin. Ensure that you are using a method suitable for the size and properties of your molecule. For example, PM3 and PM6 are semi-empirical methods that may not be accurate enough, especially for larger systems. Try using a more advanced method, such as density functional theory (DFT) with appropriate functionals and basis sets (e.g., B3LYP/6-31G), which can provide more reliable results for geometry optimizations.
4. Check the input file: Verify that your Gaussian input file is correctly formatted and includes all the necessary information, such as the molecular geometry, charge, multiplicity, optimization keywords, and basis set information. Ensure that the file extension is ".com" or ".gjf" for a Gaussian input file.
5. Consult the Gaussian documentation or support: If the above steps do not resolve the issue, it might be beneficial to consult the Gaussian software documentation, user forums, or contact their technical support for further assistance. They will be able to provide specific guidance on how to troubleshoot and resolve the error.
Remember, resolving Error 2070 might involve some trial and error, so it's important to carefully review your settings and experiment with different options to find the best approach for geometry optimization of cyclodextrin in Gaussian.