1. Errors caused by inappropriate coordinate system or geometry

Error message:

UFF calculation of energy and first derivatives.

Linear angle in Tors.

Error termination via Lnk1e in /act/apps/Gaussian16a03/g16/l402.exe at Wed Feb 23 12:26:20 2022.

Input:

#p uff opt=cartesian

scrf=(solvent=water,pcm)

0 1

O 25.11500000 22.43110000 6.97120000

O 22.62080000 23.04530000 7.53600000

O 25.11500000 26.81350000 6.97030000

O 34.24260000 32.69830000 6.97120000

O 31.74900000 33.31250000 7.53600000

Solution and Discussions:

The first thing we should try first is to set "OPT=Cartesian", which can force Gaussian to use cartesian coordinates rather than inner coordinates. However, this doesn't work for our case. After double-checking all the keywords, we take a closer look at the coordinate parameters and found that the significant digits of these parameters are too few. This can make the structure too "symmetric", and thus mislead Gaussian to determine that some bond angles are 180 degrees. An easy solution is to add a very small random number to each coordinate parameter to break the symmetry, which can be done with Excel or a few lines of python/shell codes：

0 1

O 25.1151569 22.4314123 6.971275674

O 22.62149746 23.04565043 7.536346204

O 25.11577049 26.81375715 6.971277549

O 34.24268655 32.69893546 6.972127916

O 31.74915798 33.31334506 7.53665341

WIth the new coordinate parameters, the job can run properly.

2. Errors caused by inappropriate basis-set settings

Error message:

IBasis= 50 is unrecognized in AtmBas

Input:

#p genecp empiricaldispersion=gd3 scrf=(solvent=water,pcm) b3lyp 6-31+G**

Zn-OH

-1 1

O 0.000000000 0.000000000 0.107455000

H 0.000000000 0.000000000 -0.859638000

Solution: Remove genecp. Only one basis set is used here.