.. 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