Molcas Forum

dchamb61

Member

Registered: 2022-09-01

Posts: 4

Non-Adiabatic Molecular Dynamics Considering Triplets

Hello all, and happy Monday!

I am working on a project that involves determining the photochemical mechanism of a reaction that has experimentally been shown to be more efficient when considering intersystem crossing to triplet states, as opposed to only considering triplet states.

I want to perform non-adiabatic molecular dynamics simulations on the molecule using a (10,8) active space. I want to begin the dynamics along the S1 excited state PES, and simulate intersystem crossing between singlet and triplet PES along the trajectories if possible. I've constructed a sample input file based on the following resources from the Molcas manual:

https://www.molcas.org/documentation/manual/node77.html (This page discusses the &Dynamix module and its different uses -- I constructed the input file based on the example at the bottom of the page.)

https://www.molcas.org/documentation/manual/node33.html (This page discusses the employment of Spin-Orbit Coupling using the &RASSI module, as well as computing triplet photophysics.)

I've created the following input file

>> EXPORT MOLCAS_MAXITER=10000
>> COPY $WORKDIR/$Project.velocity.xyz $WorkDir/$Project.velocity.xyz
&GATEWAY
 coord=$MOLCAS_PROJECT.xyz
 basis
 ano-s-vdzp
 Group=c1
 RICD
 AMFI

>> FOREACH ITER in (1 .. 2000)

&SEWARD
doanalytic

>> IF ( $ITER = 1 )

&RASSCF
 LumOrb
 FileOrb = $Project.StrOrb
 Spin=1
 Nactel=10 0 0
 Charge=0
 Ras1=0
 Ras2=8
 Ras3=0
 ITERATIONS=200,100
 CIRoot=2 2 1

>> COPY $Project.JobIph $Project.JobOld

>>ENDIF

&RASSCF
 JOBIPH; CIRestart
 fileorb=$Project.StrOrb
 Spin=3
 Nactel=10 0 0
 Charge=0
 Ras1=0
 Ras2=8
 Ras3=0
 ITERATIONS=200,100
 CIRoot=4 4 1
 MDRLXR=2

>>COPY $Project.JobIph $Project.JobOld

&Surfacehop
 tully
 decoherence = 0.1

&ALASKA

&Dynamix
 velver
 dt = 20
 velo = 1
 ther= 2
 temp = 300

>> End do

As this will likely be a very expensive calculation, I want to know if I have the right idea in constructing this input file based on what I want to get out of this calculation? Also, would there be any way to quantify Spin-Orbit coupling after the calculations finish? I plan on running 500 trajectories for about a picosecond.

Thank you in advance for any help you guys can provide!

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: Non-Adiabatic Molecular Dynamics Considering Triplets

I don't think SURFACEHOP supports intersystem crossings. I'd suggest you have a look at SHARC, which can use OpenMolcas for the electronic structure calculations.

dchamb61

Member

Registered: 2022-09-01

Posts: 4

Re: Non-Adiabatic Molecular Dynamics Considering Triplets

Thank you for the response Ignacio, this is extremely useful to know. You've saved me tremendous amounts of time, frustration, and computational resources in telling me this :,)