Table 2 Details of the convergence of the X2C-CASCI calculation (50 2-spinor orbitals, 28 electrons, 8.9 × 1013 2-spinor determinants) of the ground state of Rb4 (cc-pvtz-x2c141)

From: Numerically exact configuration interaction at quadrillion-determinant scale

Iteration

Active Energy (Eh)

ΔE (Eh)

\(\max \{| \Delta {C}_{i}| \}\)

∥r∥ (Eh)

1

−90.038089795466

− 

− 

4.48 × 10−2

2

−90.048919589524

1.08 × 10−2

1.21 × 10−1

1.74 × 10−2

3

−90.049940164869

1.02 × 10−3

1.64 × 10−2

4.95 × 10−3

4

−90.050002638482

6.25 × 10−5

2.53 × 10−3

1.20 × 10−3

5

−90.050006376495

3.74 × 10−6

1.37 × 10−3

2.96 × 10−4

6

−90.050006593144

2.17 × 10−7

1.55 × 10−4

7.36 × 10−5

  1. Each row corresponds to a Davidson iteration. The third and fourth columns track the changes in the computed Rayleigh-Ritz eigenpair across iterations, and the fifth column tracks the residual norm, ∥r∥ = ∥HC − EC∥, where H is the Hamiltonian, C is the CI vector, σ is their product, and E is the corresponding energy. The preconditioning dropping threshold was taken to be ε = 1.0 × 10−6. The inactive energy is -11826.102719 a.u.
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