Impact of non‐empirically tuning the range‐separation parameter of long‐range corrected hybrid functionals on ionization potentials, electron affinities, and fundamental gaps

• Published in: Journal of computational chemistry Vol. 39; no. 28; pp. 2378 - 2384
• Main Authors: Vikramaditya, Talapunur, Chai, Jeng‐Da, Lin, Shiang‐Tai
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 30.10.2018; Wiley Subscription Services, Inc
• Subjects: Affinity; electron affinity; fundamental gap; HOMO; Ionization; ionization potential; Ionization potentials; long‐range corrected hybrid functionals; LUMO; Molecular orbitals; non‐empirically tuning scheme; Parameters; range‐separation parameter; Separation; Tuning; ionization potential; HOMO; LUMO; fundamental gap; non-empirically tuning scheme; long-range corrected hybrid functionals; range-separation parameter; electron affinity
• DOI: 10.1002/jcc.25575
• ISSN: 0192-8651

Non‐empirically tuning the range‐separation parameter (ω) of long‐range corrected (LC) hybrid functionals in improving the accuracy of vertical ionization potentials (IPs), vertical electron affinities (EAs), and fundamental gaps (FGs) is investigated. Use of default ω values gives the best overall property predictions employing the Δ self‐consistent field (ΔSCF) approach, if sufficiently large basis set is used. Upon tuning, IP (HOMO) (i.e., the IP estimated from the negative of HOMO energy via DFT Koopmans’ theorem) with the IP (ΔSCF) (i.e., the IP obtained from the ΔSCF approach) the accuracy of IP (HOMO) significantly improves however a reciprocal phenomenon is not observed. An interesting observation is that EA (LUMO) (i.e., the EA estimated from the negative of LUMO energy) is more accurate than EA (ΔSCF), if the ω value is in the range of 0.30 to 0.50 bohr−1. © 2018 Wiley Periodicals, Inc. Tuning the HOMO(IP) with IP(ΔSCF) by adjusting the range separation parameter of LC‐ Hybrid Functional improves the accuracy of HOMO(IP) significantly however a vice‐versa phenomenon is not observed i.e., an improvement in accuracy of IP(ΔSCF) is not found. Impact of tuning on LUMO (EA) is negligible and its accuracy is independent of tuning. LUMO (EA) accuracy outperforms conventional EA (ΔSCF) if the range separation parameter lies within the range of 0.3 to 0.5 bohr−1. Fundamental gap (FG) follows a similar trend as that of IP.