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SebWouters / CheMPS2

CheMPS2: a spin-adapted implementation of DMRG for ab initio quantum chemistry
GNU General Public License v2.0
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Oscillator strength #47

Closed lucamontana closed 8 years ago

lucamontana commented 8 years ago

Dear Sebastian,

Can you tell me how to calculate dmrg oscillator strength of the excited states from 1-rdm ? I need to calculate dmrg optical spectrum.

Is there any possibility to plot dmrg orbitals and spin densities of excited states ?

Best wishes LUCA

SebWouters commented 8 years ago

Hi @lucamontana,

I've also added @loriab to the conversation.

What exactly do you mean with oscillator strengths?

The 1-RDM and spin-densities are accessible via

double CheMPS2::TwoDM::get1RDM_HAM( const int cnt1, const int cnt2 ) const;
double CheMPS2::TwoDM::spin_density_ham( const int cnt1, const int cnt2 ) const;

respectively, but are currently not (both) interfaced via psi4.

Best wishes, Sebastian

lucamontana commented 8 years ago

Dear Sebastian,

I mean transition probability for an excited state : https://en.wikipedia.org/wiki/Oscillator_strength . I have no clue how to calculate it myself from 1-rdm ? I am further interested how an excited state is composed of orbitals. example : S1 : homo -> lumo ; homo -1 -> lumo S2 : homo -> lumo+1 ; homo -1 -> lumo+1 .... How can i get this piece of information from 1-rdm ?

I am using the binary only. Is spin density in a cube file format (like molpro, Gaussian) available through binary ?

Best wishes LUCA

SebWouters commented 8 years ago

@lucamontana,

It's the transition 1-RDM (between the ground and excited states) you need to contract with the dipole moment.

The transition 1-RDM is not accessible in v1.7 via the binary, although it can potentially be obtained via the Hylleraas functional. If it will become available, it will be from v1.8 or later, so not at the moment.

Also the spin-density is not accessible from the binary in v1.7, only via the library.

Best wishes, Sebastian

lucamontana commented 8 years ago

Dear Sebastian,

Ok. Is there any possibility to find out the nature of excited states (i mean its orbital composition : homo -> lumo, etc ...) ?

Bests LUCA

SebWouters commented 8 years ago

Is there any possibility to find out the nature of excited states (i mean its orbital composition : homo -> lumo, etc ...) ?

Yes. You can look at the occupation numbers in the molecular orbitals (diagonal elements of the 1-particle reduced density matrix in the MO basis)...

lucamontana commented 8 years ago

OK, many thanks Sebastian. Take care. LUCA