2-particle density matrix for ccsd(t) calculation

Thank you Prof. Kallay for your help. I have run the calculation on very small system and also compared it with PySCF 2PDM from CCSD calculations.
The 2PDM from MRCC is as,
The input file is,
Here is the 2PDM from PySCF as a numpy array,
[code]array([[[[ 1.97466738e+00, -9.48766723e-17],
[-9.48766723e-17, 0.00000000e+00]],

[[-9.48766723e-17, -2.23659343e-01],
[ 0.00000000e+00, 1.07461411e-17]]],


[[[-9.48766723e-17, 0.00000000e+00],
[-2.23659343e-01, 1.07461411e-17]],

[[ 0.00000000e+00, 1.07461411e-17],
[ 1.07461411e-17, 2.53326218e-02]]]])
[\code]

I see that the OOOO and VVVV parts of the 2PDM between MRCC and PySCF matches. I am not sure about the others as I do not know the order the 2PDM is printed from MRCC. Are the numbers printed after 2PDM elements some sort of array ordering or orbital ordering? In that case, does the numbering starts from 0 right?

Thank you very much
Prasanta

 

The integers are the indices of the density matrices, running over the correlated MOs. Lines with 0 indices contain the elements of the one-particle density matrix.

Thank you Professor for your prompt and kind reply. However, I am a bit confused here. Does the program eliminates the 0 values?
In the 1PDM part, there should be n^2 = 4 elements and 1200 and 2100 indices are not printed.
Same goes for 2PDM, there should be n^4 =16 elements and only 8 are printed. And indices, such as 2 1 1 1 or say 1 2 2 2 are not printed.
Am I right here?

Also could you please suggest if I can use uncontracted and cartesian basis sets to calculate the same 2PDM at CCSD? The example I have shown above use only s-functions so the effect of cartesian basis-set is the same but I intend to use larger atoms with aug-cc-pVDZ basis set.

Yours gratefully
Prasanta

Yes, only the non-zero density matrix elements are stored in the file.
It is possible to use Cartesian and uncontracted basis sets, see keywords gauss and uncontract.

Professor, with the cartesian basis sets, I am getting this error. I was using this version, Release date: August 28, 2023.

basis=STO-3G
calc=CCSD
mem=500MB
dens=2
gauss=Cart
uncontract=on
geom=xyz
2

H 0.00000000 0.00000000 0.37000203
H 0.00000000 0.00000000 -0.37000202



Checking keyword combinations...

Analytic derivatives are not available with Cartesian Gaussians!

Fatal error in exec minp.
Program will stop.

************************ 2025-01-06 10:42:51 *************************
Error at the termination of mrcc.
**********************************************************************

Is there any way around in the newest version or even the older version?