last updated Thursday, September 20, 2007

Here is a list of a few commonly observed problems and how to fix them.

Problem Possible Solution(s)
The calculation fails with an error message. Go to Output and check for a more detailed error message 1. If the calculation ran out of cycles, just re-submit the calculation. Often times this occurs is there are small changes observed towards the end and the program is not able to find a "true" minimum.
2. If a multiplicity error occured, check for the correct multiplicity in the setup calculation menu. If this is set correctly, double-check your structure. It is not uncommon that a hydrogen atom(s) is (are) deleted accidently or the number of atoms attached is too high.
The calculation seems to take forever. 1. Make sure that only one window is active. If this is the case, check if the calculation is still running using the monitor window (upper left corner). Active calculations appear in this window.
2. The energy cannot be minimized since the structure is very flexible. The program is going back and forth between two values without finding a true minimum.
The obtained data looks weird. 1. One of the most common problems of these calculations is to verify how reliable the obtained data is. This is where the scientist comes in (here: you!) who has to develop a reasonable model to explain the data based on his knowledge and experience.
2. The calculation was improperly set up (wrong molecule, wrong method, etc) and did not yield the desired information. Double-check these parameters.