Throughout this documentation, we employ terms and abbreviations which may not be immediately clear to the new user. Herein is a compiled list of important terms accompanied by brief descriptions. Further discussion for many of these terms is included in the user documentation.
In order to take into account the environmental energetical contributions to an excited molecule inside a crystal, we offer several kinds of non-intrusive embedding methods:
.. glossary::
ONIOM
Our own N-layered Integrated molecular Orbital and Molecular
mechanics. An extrapolative (subtractive) embedding paradigm for multilevel
calculations\ :cite:`Dapprich1999,Maseras1995,Humbel1996`
EC
Embedded Cluster. The application of the ONIOM method with
electrostatic embedding to a cluster of molecules taken from their crystalline
positions
EEC
Ewald Embedded Cluster. Similar to EC but using an electrostatic
embedding scheme aimed at reproducing the Ewald potential of the crystal
SC-EEC
Self-Consistent Ewald Embedded Scheme. The EEC model where the
embedding charges are computed self consistently
Mechanical embedding
ONIOM embedding where no point charges are included and the intersystem
electrostatic interaction is purely at low level
Electrostatic embedding
ONIOM embedding where the point charges from the surrounding cluster are
included in the Hamiltonian of the high level of theory to be treat
Coulombic terms in the excited state
In the expression of the 2-level ONIOM energy, the system under scrutiny is partitioned into two regions:
.. glossary::
Model system
The central molecule(s) whose properties are under scrutiny
Real system
The complete cluster of molecules taken from their
crystalline positions, including and surrounding the model system
By nature, 2-level ONIOM combines two levels of theory:
.. glossary::
High level
A level of theory which describes the required properties of
the model system. In photochemistry this will often be an excited state method
Low level
A less computationally expensive level of theory than the high
level. This will typically be a ground state method
When optimising the geometry of a molecule using one of the cluster models, a few concurrent calculations must be carried out.
.. glossary::
mh
Model system high level calculation
ml
Model system low level calculation
rl
Real system low level calculation
mg
Model system calculation in the ground state of the high level
.. glossary::
MECI
Minimum Energy Conical Intersection. The minimum energy point in the
crossing seam between potential energy surfaces. This point is located in
**fromage** by using the penalty function method.\ :cite:`Levine2008`
Exciton coupling
A measure of the splitting of the excited state energy levels due to the
formation of a molecular dimer\ :cite:`Arag2015`