The DIRAC code for relativistic molecular calculations

Abstract

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Exact quasi-relativistic wavefunctions of Hydrogen-like atoms

“…(14), (16), and (25), then ρo can be obtained using Eqs. (23) and (24). After τ(ρ) is found for given values of n and l, χ(ρ) can be obtained using Eq.…”

“…This requires a bispinor wavefunction with 4 components 2, [15][16][17][18] . However, there are approximated theories only requiring, for the description of the spin effects, spinor two-component wavefunctions 2,[15][16][17][18][19][20][21][22][23] . In this work, the attention is focused on the consequences resulting, from including the correct relativistic relation between K and p, for the quantum theory of Hydrogen-like atoms.…”

Ground and excited electronic states of AuH2via detachment energies on AuH2− using state-of-the-art relativistic calculations

“…Unless otherwise stated, all the reported calculations have been carried out using the relativistic quantum chemistry code DIRAC 42,43 (release 2018) which implements all the methods mentioned above in combination with accurate relativistic Hamiltonians. In particular, in order to investigate the impact of relativistic effects on VDEs we employed exact 2-component [44][45][46][47][48] (X2C) and 4-component (4c) Hamiltonians, with the latter also in its spinfree (SF) form 49 .…”

“…The SCF convergence on the excited state of the AuH 2 molecule was obtained by overlap selection. 42,43 Correlated EOM-IP-CCSD calculations are based on the recent relativistic formulation 29 and have been carried out using both Dyall valence (dyall.vdz, dyall.vtz, dyall.vqz) and core-valence (dyall.cvdz, dyall.cvtz, dyall.cvqz) basis sets 50,51 . For the former calculations the 5s, 5p, 5d and 6s electrons for Au are correlated, whereas for the latter the n=4 shell electrons of Au were included in the active space as well.…”

Finite-Field Calculations of Transition Properties by the Fock Space Relativistic Coupled Cluster Method: Transitions between Different Fock Space Sectors

“…We bypassed this difficulty via choosing quite large sets of active particle spinors and using the adjustable denominator shift technique [43] to suppress the possible divergencies in the presence of intruder states (more specifically, we employed the simulated imaginary shifts [32]). To conserve the core separability of the original FS RCC scheme, shifts were never applied to the energy denominators in the equations for T (0h0p) amplitudes; a balanced treatment of excitation and deexcitation contributions to PΩP implied the use of non-shifted equations for T The construction of spinors and evaluation of one-and two-electron integrals was performed using the DIRAC19 program package [15,44] whereas all FS RCC calculations were carried out with the help of the EXP-T code [45][46][47]. The VIBROT code [48] was used to solve the vibrational problem and compute the excited-state lifetime of TlF.…”