Introduction
************

MOPAC [1] is a general-purpose semiempirical quantum chemistry engine
for the study of molecular and periodic structures. A good trade-off
between speed and accuracy is achieved through a minimal basis and
parameterization against experimental data, with parameters for most
elements.

As of the 2026.1 release of the Amsterdam Modeling Suite, MOPAC has
become an engine in the new AMS driver setup. If you have not done so
yet, we highly recommend you to first read the General section of the
AMS Manual. In practice the inclusion of MOPAC into AMS means that
MOPAC can now be used for many applications that were previously not
supported:

* Linear transit and PES scan

* Constrained geometry optimizations

* Molecular dynamics simulations

* Lattice optimization (also under pressure)

* Elastic tensor and related properties (e.g. Bulk modulus)

* Phonon calculations

* ...

Please refer to the AMS manual for a complete overview.


What's new in MOPAC 2019
========================

* MOPAC has been fully integrated as an Engine in the Amsterdam
  Modeling Suite; this significantly speeds up the execution of MOPAC
  via AMS.

* Parallel binaries.

New input options (also available via the Graphical User Interface):

* Calculation of pKa

* COSMO: all solvents available in ADF/Band are now also available in
  MOPAC.

* Static polarizability tensor

* Localized orbitals (Natural Bond Orbitals)

* SCF options: Camp-King converger, ...
