.. index::
single: Program; MCLR
single: MCLR
.. _TUT\:sec\:mclr:
:program:`MCLR` --- A Program for Linear Response Calculations
==============================================================
:program:`MCLR` computes response calculations on single and multiconfigurational
SCF wave functions. One of the basic uses of :program:`MCKINLEY` and :program:`MCLR`
is to compute analytical Hessians (vibrational frequencies, IR intensities, etc).
:program:`MCLR` can also calculate the Lagrangian multipliers for
a MCSCF state included in a state average optimization and construct the effective
densities required for analytical gradients of such a state.
The use of keyword :kword:`RLXRoot` in the :program:`RASSCF` program is required.
In both cases the explicit request of executing the :program:`MCLR` module is not
required and will be automatic.
We postpone further
discussion about :program:`MCLR` to :numref:`TUT:sec:structure`.
It follows an example of how to optimize an excited state from a previous
State-Average (SA) CASSCF calculation.
.. extractfile:: tutorials/MCLR.acrolein.input
&GATEWAY
Title= acrolein minimum optimization in excited state 2
Coord=$MOLCAS/Coord/Acrolein.xyz
Basis= sto-3g
Group=NoSym
>>> Do while
&SEWARD
&RASSCF
Title= acrolein
Spin= 1; nActEl= 6 0 0; Inactive= 12; Ras2= 5
CiRoot= 3 3 1
Rlxroot= 2
&SLAPAF
>>> EndDo
The root selected for optimization has been selected here with the keyword
:kword:`Rlxroot` in :program:`RASSCF`, but it is also possible to select it
with keyword :kword:`SALA` in :program:`MCLR`.
Now if follows an example as how to compute the analytical hessian for the lowest
state of each symmetry in a CASSCF calculation (SCF, DFT, and RASSCF analytical
Hessians are also available).
.. extractfile:: tutorials/MCLR.benzoquinone.input
&GATEWAY
Title=p-benzoquinone anion. Casscf optimized geometry.
Coord = $MOLCAS/Coord/benzoquinone.xyz
Basis= sto-3g
Group= X Y Z
&SEWARD
&RASSCF
TITLE=p-benzoquinone anion. 2B3u state.
SYMMETRY=2; SPIN=2; NACTEL=9 0 0
INACTIVE=8 0 5 0 7 0 4 0
RAS2 =0 3 0 1 0 3 0 1
&MCKINLEY; Perturbation=Hessian
The :program:`MCLR` is automatically called after :program:`MCKINLEY`
and it is not needed in the input.
:program:`MCLR` program --- Basic and Most Common Keywords
----------------------------------------------------------
.. class:: keywordlist
:kword:`SALA`
Root to relax in geometry optimizations
:kword:`ITER`
Number of iterations