Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

摘要: The extended second order algebraic-diagrammatic construction (ADC(2)-x) scheme for the polarization operator in combination with core-valence separation (CVS) approximation is well known to be a powerful quantum chemical method calculation of core-excited states and description X-ray absorption spectra. For first time, implementation results third approach CVS-ADC(3) are reported. Therefore, CVS has been applied ADC(3) working equations resulting terms have implemented efficiently adcman program. By treating α β spins separately from each other, unrestricted variant CVS-UADC(3) treatment open-shell systems as well. performance accuracy demonstrated respect set small middle-sized organic molecules. obtained at level compared CVS-ADC(2)-x values experimental data by calculating complete basis limits. influence sets further investigated employing large different sets. Besides core-excitation energies oscillator strengths, importance cartesian functions orbital relaxation effects analyzed this work computational timings. It turns out that level, not improved data, because fortuitous error compensation inherent broken. While overestimates core excitation on average 0.61% ± 0.31%, provides an averaged underestimation −0.22% 0.12%. Eventually, best agreement experiments can achieved using diffuse least triple-ζ level.