# Introduction¶

UFF (Universal Forcefield) is a full periodic table forcefield that can be used to calculate single point energies, do geometry optimizations, calculate frequencies, etc... It is also the default pre-optimizer in the Graphical User interface (GUI) to clean up manualy drawn structures. UFF can also do calculations with chain, slab or bulk periodicity. For details on the inner workings of the forcefield, see the 1992 paper by Rappe et al. [1].

## UFF-GUI¶

Note that the graphical user interface UFF-GUI enables all users to set up UFF calculations with a few mouse clicks. When using UFF, also for pre-optimizing, it is important to remember that any forcefield method relies on a set of parameters. This means that even though UFF supports all elements up to Z=103, it might not generate the desired structures for uncommon oxidation states in metallic structures. If this is the case, you could add new parameters to UFF or attach dummy hydrogen atoms to the metal atom.

## What’s new in UFF 2018¶

### New features¶

• Elastic tensor and related properties (e.g. Bulk modulus) (via AMS)
• Linear transit and PES scan (via AMS)
• Lattice optimization (via AMS)
• Geometry optimization under pressure (via AMS)
• More Molecular Dynamics options (via AMS)

### AMS: a new driver program¶

Important

In the 2018 release of the Amsterdam Modeling Suite we introduced a new driver program call AMS. We recommend you to first read the General section of the AMS Manual

If you use UFF exclusively via the Graphical User Interface (GUI), this change should not create any issues. If, on the other hand, you create input files by hand (or you use UFF via PLAMS), then you should be aware that shell scripts for UFF-2017 and previous versions are not compatible with UFF-2018 and have to be adjusted to the new setup.

The example below shows how a shell script for UFF-2017 is converted to UFF-2018.

UFF-2017 shell script (obsolete):

#!/bin/sh

# This is a shell script for UFF-2017 which will not work for UFF-2018

$ADFBIN/uff << eor Task RunType GO End System Atoms H 0.0 0.0 0.0 H 0.9 0.0 0.0 End End Geometry End eor  UFF-2018 shell script: #!/bin/sh # This is a shell script for UFF-2018 # The executable '$ADFBIN/UFF' is no longer present.
# You should use '$ADFBIN/ams' instead.$ADFBIN/ams <<eor
# Input options for the AMS driver:

System
Atoms
H 0.0 0.0 0.0
H 0.9 0.0 0.0
End
End

# The input options for UFF, which are described in this manual,
# should be specified in the 'Engine UFF' block:

Engine UFF
EndEngine
eor