# Re: CASPT2 convergence

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Posted by Roser on March 09, 2015 at 15:42:27:

In Reply to: Re: CASPT2 convergence posted by Steven Vancoillie on January 17, 2015 at 20:18:04:

Hello,

I have a new question: What does the CASPT2 iteration do?
A perturbation does not need an iterative procedure. I have read in the manual: "Of course, the complete Hˆ0 is used to solve the CASPT2 equations, which is why an iterative procedure is needed. "
What is the program doing?
Thank you.

And you asked for the output (sorry for the delay). I copy the state without convergence (not all iterations). If you need something more to understand the out just tell me.

Thank you again.

Roser Morales

Output:

++ CASPT2 computation 19

********************************************************************************
Multi-State initialization phase begins for group 19
--------------------------------------------------------------------------------
********************************************************************************
Compute H0 matrices for state 19
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
H0 matrices have been computed.

********************************************************************************
CASPT2 EQUATION SOLUTION
--------------------------------------------------------------------------------
Total nr of CASPT2 parameters:
Before reduction: 852699231
After reduction: 851961627

The contributions to the second order correlation energy in atomic units.
-----------------------------------------------------------------------------------------------------------------------------
IT. VJTU VJTI ATVX AIVX VJAI BVAT BJAT BJAI TOTAL RNORM
-----------------------------------------------------------------------------------------------------------------------------
1 -0.002144 -0.000001 -0.008168 -0.013210 -0.006356 -0.466291 -0.363396 -4.328890 -5.188456 0.673122
2 -0.001326 -0.000001 -0.008262 -0.012690 -0.006175 -0.465530 -0.362861 -4.328319 -5.185164 2.535599
3 -0.001947 -0.000001 -0.008185 -0.013078 -0.006324 -0.466129 -0.363296 -4.328787 -5.187746 0.796509
4 -0.001272 -0.000001 -0.008258 -0.012720 -0.006183 -0.465249 -0.362825 -4.328329 -5.184835 0.871615
5 -0.003803 -0.000001 -0.008087 -0.014415 -0.006509 -0.467549 -0.363968 -4.329413 -5.193745 13.163524
6 -0.001114 -0.000001 -0.008260 -0.012595 -0.006178 -0.465149 -0.362796 -4.328310 -5.184404 1.244665
7 -0.001808 -0.000001 -0.008187 -0.012961 -0.006318 -0.466058 -0.363271 -4.328768 -5.187372 0.687592
8 0.000359 -0.000001 -0.008372 -0.011826 -0.005961 -0.462112 -0.361749 -4.327515 -5.177176 6.005586
9 -0.001818 -0.000001 -0.008180 -0.012948 -0.006332 -0.466081 -0.363305 -4.328809 -5.187474 0.581183
10 -0.002959 -0.000001 -0.008115 -0.013538 -0.006462 -0.470398 -0.364404 -4.329409 -5.195285 2.854411
...
...
...
398 -0.001906 -0.000001 -0.008192 -0.013170 -0.006310 -0.467340 -0.363510 -4.328815 -5.189243 0.095900
399 -0.001875 -0.000001 -0.008186 -0.013190 -0.006320 -0.467195 -0.363387 -4.328764 -5.188917 0.097536
400 -0.001911 -0.000001 -0.008191 -0.013164 -0.006310 -0.467315 -0.363484 -4.328798 -5.189175 0.139164

NOT CONVERGED AFTER MAX ITERATIONS.
-------------------------------------------------------------------------------------------------------------------

FINAL CASPT2 RESULT:

Reference energy: -14659.6439463183
E2 (Non-variational): -5.1891747944
E2 (Variational): -5.1892225852
Total energy: -14664.8331689035
Residual norm: 0.1391642896
Reference weight: 0.33062

Contributions to the CASPT2 correlation energy
Active & Virtual Only: -0.4755062560
One Inactive Excited: -0.3785588992
Two Inactive Excited: -4.3351096392

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if B is 1s22s22p1, what is Li?

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