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You can choose an avatar and change the default style by going to "Profile" → "Personality" or "Display".#1 2024-04-20 15:22:46
- FedCpp
- Member
- Registered: 2020-12-07
- Posts: 4
Doubts about reference weight in CASPT2 calculations
I'm performing a CASSCF/CASPT2 calculation on an aromatic system with 182 electrons (24 of which are pi-electrons) in the gas phase,
and I need to characterize its absorption spectrum.
I'm performing various tests considering different active spaces, using the default options (i.e., IPEA 0.25).
Unfortunately, I notice that the reference weight in the CASPT2 state is low.
For example, for a CASPT2 calculation on top of SA(8)/CASSCF(6,6)/6-31G**, I find:
Reference weight: 0.44286
Reference weight: 0.43781
Reference weight: 0.43479
Reference weight: 0.43581
Reference weight: 0.43422
Reference weight: 0.43414
Reference weight: 0.43441
Reference weight: 0.42728
For the root 1 for example:
Computing the right-hand side (RHS) elements
--------------------------------------------
Using RHSALL2+ADDRHS algorithm
Variance of |WF0>: 12.0088395650
The contributions to the second order correlation energy in atomic units.
-----------------------------------------------------------------------------------------------------------------------------
IT. VJTU VJTI ATVX AIVX VJAI BVAT BJAT BJAI TOTAL RNORM
-----------------------------------------------------------------------------------------------------------------------------
1 -0.004192 -0.010342 -0.008266 -0.094946 -0.178485 -0.021610 -0.346153 -2.856568 -3.520562 0.003291
2 -0.004225 -0.010393 -0.008309 -0.095218 -0.178656 -0.021659 -0.346322 -2.856804 -3.521587 0.000335
3 -0.004224 -0.010395 -0.008308 -0.095231 -0.178664 -0.021661 -0.346330 -2.856809 -3.521622 0.000033
4 -0.004224 -0.010395 -0.008308 -0.095230 -0.178662 -0.021661 -0.346328 -2.856807 -3.521613 0.000003
Correlation energy /Case, /Symm, and sums:
VJTU -0.00422385 -0.00422385
VJTIP -0.00872812 -0.00872812
VJTIM -0.00166670 -0.00166670
ATVX -0.00830767 -0.00830767
AIVX -0.09522970 -0.09522970
VJAIP -0.08322757 -0.08322757
VJAIM -0.09543444 -0.09543444
BVATP -0.01850275 -0.01850275
BVATM -0.00315799 -0.00315799
BJATP -0.15413198 -0.15413198
BJATM -0.19219570 -0.19219570
BJAIP -1.78469886 -1.78469886
BJAIM -1.07210776 -1.07210776
Summed: -3.52161308 -3.52161308
-----------------------------------------------------------------------------------------------------------------------------
FINAL CASPT2 RESULT:
Reference energy: -1034.1609110920
E2 (Non-variational): -3.5216130847
Shift correction: -0.0353390117
E2 (Variational): -3.5569520964
Total energy: -1037.7178631884
Residual norm: 0.0000003521
Reference weight: 0.44286
Contributions to the CASPT2 correlation energy
Active & Virtual Only: -0.0299684087
One Inactive Excited: -0.4457812241
Two Inactive Excited: -3.0458634519
++ Denominators, etc.
--------------------------------------------------------------------------------------------------------------
Report on small energy denominators, large coefficients, and large energy contributions.
The ACTIVE-MIX index denotes linear combinations which gives ON expansion functions
and makes H0 diagonal within type.
DENOMINATOR: The (H0_ii - E0) value from the above-mentioned diagonal approximation.
RHS VALUE : Right-Hand Side of CASPT2 Eqs.
COEFFICIENT: Multiplies each of the above ON terms in the first-order wave function.
Thresholds used:
Denominators: 0.3000
Coefficients: 0.0250
Energy contributions: 0.0050
CASE SYMM ACTIVE-MIX NON-ACTIVE INDICES DENOMINATOR RHS VALUE COEFFICIENT CONTRIBUTION
AIVX 1 Mu1.0002 In1.088 Se1.095 0.71452322 -0.02916399 0.03633980 -0.00105981
AIVX 1 Mu1.0010 In1.088 Se1.095 0.81134512 0.03985521 -0.04509153 -0.00179713
AIVX 1 Mu1.0016 In1.088 Se1.095 0.85614522 -0.02392402 0.02640851 -0.00063180
AIVX 1 Mu1.0018 In1.088 Se1.095 0.88448935 -0.02918559 0.03140910 -0.00091669
AIVX 1 Mu1.0012 In1.086 Se1.098 0.94402266 -0.03589174 0.03576130 -0.00128354
VJAIM 1 Mu1.0002 Se1.096 In1.087 In1.086 0.94221988 0.02720961 -0.02680031 -0.00072923
BVATP 1 Mu1.0003 Se1.096 Se1.096 0.86100626 -0.03107640 0.03313801 -0.00102981
BVATP 1 Mu1.0003 Se1.098 Se1.098 0.95657805 -0.02777542 0.02728972 -0.00075798
BJATM 1 Mu1.0002 In1.087 Se1.098 Se1.096 0.95707837 -0.05067670 0.04973331 -0.00252032
BJAIP 1 Se1.095 In1.085 Se1.095 In1.085 0.98684735 0.02735369 -0.02624597 -0.00071792
BJAIP 1 Se1.097 In1.085 Se1.097 In1.085 1.09552058 0.03456875 -0.03133476 -0.00108320
BJAIP 1 Se1.096 In1.087 Se1.096 In1.087 0.96121674 0.03380285 -0.03293962 -0.00111345
BJAIP 1 Se1.095 In1.088 Se1.095 In1.088 0.87855162 0.04606607 -0.04853729 -0.00223592
BJAIP 1 Se1.097 In1.088 Se1.097 In1.088 0.98722485 0.02703315 -0.02595438 -0.00070163
BJAIM 1 Se1.095 In1.085 Se1.096 In1.088 0.98703610 0.05394989 -0.05203567 -0.00280732
--
--But the energy and character of the first two excited states I'm interested in are satisfactory with experiments.
The same happens if I increase the active space (SA(8)/CASSCF(8,8)), the Reference weight is below 0.5 for all roots.
Are there any suggestions?
Thanks to anyone who will help me.
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#2 2024-04-22 08:00:20
- Ignacio
- Administrator
- From: Uppsala
- Registered: 2015-11-03
- Posts: 1,011
Re: Doubts about reference weight in CASPT2 calculations
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