Table 3 Details of the convergence of the X2C-CASCI calculation (60 2-spinor orbitals, 12 electrons, 1.4 × 1012 2-spinor determinants) of the ground state of Xe2 (x2c-TZVPall-2c96)

From: Numerically exact configuration interaction at quadrillion-determinant scale

Iteration

Active Energy (Eh)

ΔE (Eh)

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

∥r∥ (Eh)

1

−21.059579374232

− 

− 

4.76 × 10−1

2

−21.194173478231

1.35 × 10−1

3.90 × 10−2

1.86 × 10−1

3

−21.206728805229

1.26 × 10−2

8.89 × 10−3

5.62 × 10−2

4

−21.207569776081

8.41 × 10−4

8.74 × 10−4

1.75 × 10−2

5

−21.207634517148

6.47 × 10−5

4.51 × 10−4

7.88 × 10−3

6

−21.207644283591

9.77 × 10−6

1.19 × 10−4

4.48 × 10−3

7

−21.207646647756

2.36 × 10−6

3.90 × 10−5

2.93 × 10−3

  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 × 10−5. The inactive energy is −14868.439049 a.u.
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