Multiwfn forum

prasanta13

Member

Registered: 2018-12-30

Posts: 41

Calculate the one-particle and two-particle density matrix

Hi Prof Tian,
I am trying to obtain the HF and CCSD(T) one and two-particle density matrix from the respective wavefunction (like HF or Correlated). I can do this using PySCF, but it takes a lot of memory (1TB for ~200 basis functions for CCSD(T)). This is why I tried to do it with other programs like Psi4 or ORCA which are less memory hungry. However, I do not know how to obtain the DM from wfn file. Note: I am using a custom basis functions.
Thanks
Prasanta

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Calculate the one-particle and two-particle density matrix

Dear Prasanta,

I don't have much experience in extracting 2RDM. If you only need 1RDM for CCSD(T), I suggest using PSI4, the steps are described in Section 4.A.8 of Multiwfn manual.

Tian

prasanta13

Member

Registered: 2018-12-30

Posts: 41

Re: Calculate the one-particle and two-particle density matrix

Many many thanks Prof Tian. I am working with PSI4, Lets see if I can find something.

jxzou

Member

Registered: 2023-09-11

Posts: 7

Re: Calculate the one-particle and two-particle density matrix

Please note that (un)relaxed density of CCSD(T) in PySCF are problematic currently. The problem occurs at the (T) step, while the CCSD density is correct. See the PySCF github issue https://github.com/pyscf/pyscf/issues/1272.

My personal recommendation is to use Molpro or PSI4. Also note that CCSD(T) density is not supported in ORCA (so far for all 5.x).

prasanta13

Member

Registered: 2018-12-30

Posts: 41

Re: Calculate the one-particle and two-particle density matrix

Sorry for the late reply, I am incredibly sorry.
I have asked the PSI4 community to extract 2PDM at CCSD(T) level. However, I got nothing yet. Could you tell me how to obtain the 2PDM from the CCSD(T) calculation from PSI4 (preferred since I can access it) or Molpro.

Thanking You
Prasanta