Dear all, I'm new to MESMER. I would like to calculate the intersystem crossing (ISC) rate by LandauZenerCrossing mehtod implemented in MESMER. I have calculated the geometries and frequencies of reactant, product, and MECP using CASPT2//CASSCF of OpenMolcas software. However, I'm not sure how to obtain the "GradientReducedMass" and "GradientDifferenceMagnitude" needed for ISC rate calculation. According to the MESMER manual, GradientReducedMass means the reduced mass for movement along the direction orthogonal to the crossing seam, and GradientDifferenceMagnitude means the norm of the vector representing the gradient difference at the MECP. I found two papers ( DOI:10.1039/B211871H, DOI:10.1002/qua.25124) dicussed these parameters, but I still don't have a clue. Could these parameters obtained by quantum mechanical software like OpenMolcas, or do I have to use other program to calculate? Thanks in advance.
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Firstly, my apologies for taking so long to respond, I have been trying to get details from colleagues but have so far been unsuccessful.
The implementation of the Landau-Zener (LZ) transition in MESMER is based on earlier code developed by Jeremy Harvey, a paper by whom you cite above. Looking through the papers, the code and comparing with the derivation of the LZ transition, the "GradientReducedMass" is the reduced mass associated with the reaction coordinate, so I would suggest that a reasonable first approximation might be the reduced mass of the mode that most closely corresponds to motion along the reaction coordinate. Following, Lykhin et al. this mode appears to be given by the normalized Delta G vector, so the appropriate mass weighting of this vector should give the reduced mass.
You will need the Delta G vector again as this is the "GradientDifferenceMagnitude" parameter and you should be able to obtain this from your calculation of the MECP, following the paper of Lykhin et al., it is the norm of the difference between the potential gradients, or classical forces, at the MECP, that is the norm of Delta G. I think these forces should be straightforward to obtain from OpenMolcas.
I will keep searching for better definitions and forward anything that I find and if you should find better definitions I would appreciate it if you would share them with me.
I hope this is of some help.
With regards, Struan
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Dear all, I'm new to MESMER. I would like to calculate the intersystem crossing (ISC) rate by LandauZenerCrossing mehtod implemented in MESMER. I have calculated the geometries and frequencies of reactant, product, and MECP using CASPT2//CASSCF of OpenMolcas software. However, I'm not sure how to obtain the "GradientReducedMass" and "GradientDifferenceMagnitude" needed for ISC rate calculation. According to the MESMER manual, GradientReducedMass means the reduced mass for movement along the direction orthogonal to the crossing seam, and GradientDifferenceMagnitude means the norm of the vector representing the gradient difference at the MECP. I found two papers ( DOI:10.1039/B211871H, DOI:10.1002/qua.25124) dicussed these parameters, but I still don't have a clue. Could these parameters obtained by quantum mechanical software like OpenMolcas, or do I have to use other program to calculate? Thanks in advance.
Dear Jianqin Qian,
Thank-you for your message. I will confer with colleagues and respond shortly.
With regards, Struan
Dear Jianqin Qian,
Firstly, my apologies for taking so long to respond, I have been trying to get details from colleagues but have so far been unsuccessful.
The implementation of the Landau-Zener (LZ) transition in MESMER is based on earlier code developed by Jeremy Harvey, a paper by whom you cite above. Looking through the papers, the code and comparing with the derivation of the LZ transition, the "GradientReducedMass" is the reduced mass associated with the reaction coordinate, so I would suggest that a reasonable first approximation might be the reduced mass of the mode that most closely corresponds to motion along the reaction coordinate. Following, Lykhin et al. this mode appears to be given by the normalized Delta G vector, so the appropriate mass weighting of this vector should give the reduced mass.
You will need the Delta G vector again as this is the "GradientDifferenceMagnitude" parameter and you should be able to obtain this from your calculation of the MECP, following the paper of Lykhin et al., it is the norm of the difference between the potential gradients, or classical forces, at the MECP, that is the norm of Delta G. I think these forces should be straightforward to obtain from OpenMolcas.
I will keep searching for better definitions and forward anything that I find and if you should find better definitions I would appreciate it if you would share them with me.
I hope this is of some help.
With regards, Struan