3.4 Performing multi-state CASPT2 calculations.
3.4.1 Prepare and submit all MS-CASPT2 calculations using the program CASPT2.
Goal: including dynamic electron correlation by a second order perturbation method where the CASSCF states are the zero order. Only valence electron correlation. Note that Ln 5s5p shells must be considered valence. “Frozen” in this context means: no excitations will be allowed from the frozen shells. Core shells should not be correlated. Hence Ce 1-4s,2-4p,3-4d; F 1s should be frozen. Translate that to symmetry MOs and check: Frozen 9 4 4 3 4 3 3 1.
In Ce3+ we will do a MS-CASPT2 calculation over the whole block because the mixing of irreps due to broken symmetry is negligible. This will be different in the Pr case, where we will do MS-CASPT2 calculations for sub-blocks containing Oh irreps only.
In directory inputs/CASPT2, check file ms-caspt2.input.
Submit the block-dependent MS-CASPT2 calculations for all points in the dCe−F grid. For that, in the shells directory: Edit j.calculation and uncomment only the “ksh run.caspt2.sh $Block $ms-roots $Caspt2Dir” lines of the target blocks. Invoke prepare.jobs to prepare all the job files, update do.submit, and invoke it to submit all the jobs.
3.4.2 Analyze and plot the results of CASPT2.
Go to directory printouts/CASPT2.
Grep the rc= value in all printouts. It should be 0. Check some printouts (e.g. reference energy should be the rasscf one).
Use the CASPT2 analyzers to assign the D2h states to Oh irreps and to partially prepare input for EFIT program.
Update and invoke do.analyze.ms-caspt2. This script shell links the $Block.rasscf.assignments files in the RASSCF print- outs directory ../RASSCF and calls the analyzer shells/pre-post/analyze.ms-caspt2.ksh,
which uses the files:
*.$Block.*.caspt2.output
$Block.rasscf.assignments
and produces the files:
*.summary, which are useful to detect errors if something goes wrong
*.MS.efit.dat files for EFIT
$Block.ms-caspt2.assignments, which must be checked
*.$Block.*.msin.energies which will be used to prepare the input of sub-sequent RASSI-SO calculations
some other files that will not be used in the present procedure
Use EFIT to fit the MS-CASPT2 energy curves and to prepare input to plot them.
Go to the results directory.
Update MS.efit.inp.head and prep.MS.efit and run the latter. Check file MS.efit.out.
To plot the MS-CASPT2 energy curves, run XMGRACE, open Ce.RAS.PT2.SO.agr, and import MS.curves.txt in the window of the MS-CASPT2 results.
Edit MS.efit.inp and run “efit.ksh MS” until the fitting of the energy curves has a good quality. The data in MS.efit.out immediately after the keyword SUMMARY will be later read to make a LATEX table in a report. Substitute the input data after the keyword INPUT DATA in MS.efit.inp by that in eordered.efit.inp if increasing energy order is the choice to prepare the table of CASSCF and MS-CASPT2 results next.
3.4.3 Make a basic report with the CASSCF and MS-CASPT2 results.
Make the body of a LATEX table that combines CASSCF and MS-CASPT2 spectroscopic constants calculated with EFIT.
In the results directory, run do.SF.table. It will combine the spectroscopic constants in rasscf.efit.out and MS.efit.out and produce the core of a useful LATEX table in SF.table.tex.dat.
Make the report.
In the results/latex directory, issue make. It will make the report in report.pdf, which can be visualized.
Conclude on the dynamic electron correlation effects by comparing MS-CASPT2 results (with) and CASSCF results (without).