TY - JOUR

T1 - Assessment of time-dependent density functional schemes for computing the oscillator strengths of benzene, phenol, aniline, and fluorobenzene

AU - Miura, Masanori

AU - Aoki, Yuriko

AU - Champagne, Benoit

PY - 2007/9/7

Y1 - 2007/9/7

N2 - In present study the relevance of using the time-dependent density functional theory (DFT) within the adiabatic approximation for computing oscillator strengths (f) is assessed using different LDA, GGA, and hybrid exchange-correlation (XC) functionals. In particular, we focus on the lowest-energy valence excitations, dominating the UV/visible absorption spectra and originating from benzenelike HOMO(π) →LUMO (π) transitions, of several aromatic molecules: benzene, phenol, aniline, and fluorobenzene. The TDDFT values are compared to both experimental results obtained from gas phase measurements and to results determined using several ab initio schemes: random phase approximation (RPA), configuration interaction single (CIS), and a series of linear response coupled-cluster calculations, CCS, CC2, and CCSD. In particular, the effect of the amount of Hartree-Fock (HF) exchange in the functional is highlighted, whereas a basis set investigation demonstrates the need of including diffuse functions. So, the hybrid XC functionals-and particularly BHandHLYP-provide f values in good agreement with the highly correlated CCSD scheme while these can be strongly underestimated using pure DFT functionals. These results also display systematic behaviors: (i) larger f and squares of the transition dipole moments (∫μ∫2) are associated with larger excitation energies (ΔE); (ii) these relationships present generally a linear character with R0.9 in least-squares fit procedures; (iii) larger amounts of HF exchange in the XC functional lead to larger f, ∫μ∫2, as well as ΔE values; (iv) these increases in f, ∫μ∫2, and ΔE are related to increased HOMO-LUMO character; and (v) these relationships are, however, not universal since the linear regression parameters (the slopes and the intercepts at the origin) depend on the system under investigation as well as on the nature of the excited state.

AB - In present study the relevance of using the time-dependent density functional theory (DFT) within the adiabatic approximation for computing oscillator strengths (f) is assessed using different LDA, GGA, and hybrid exchange-correlation (XC) functionals. In particular, we focus on the lowest-energy valence excitations, dominating the UV/visible absorption spectra and originating from benzenelike HOMO(π) →LUMO (π) transitions, of several aromatic molecules: benzene, phenol, aniline, and fluorobenzene. The TDDFT values are compared to both experimental results obtained from gas phase measurements and to results determined using several ab initio schemes: random phase approximation (RPA), configuration interaction single (CIS), and a series of linear response coupled-cluster calculations, CCS, CC2, and CCSD. In particular, the effect of the amount of Hartree-Fock (HF) exchange in the functional is highlighted, whereas a basis set investigation demonstrates the need of including diffuse functions. So, the hybrid XC functionals-and particularly BHandHLYP-provide f values in good agreement with the highly correlated CCSD scheme while these can be strongly underestimated using pure DFT functionals. These results also display systematic behaviors: (i) larger f and squares of the transition dipole moments (∫μ∫2) are associated with larger excitation energies (ΔE); (ii) these relationships present generally a linear character with R0.9 in least-squares fit procedures; (iii) larger amounts of HF exchange in the XC functional lead to larger f, ∫μ∫2, as well as ΔE values; (iv) these increases in f, ∫μ∫2, and ΔE are related to increased HOMO-LUMO character; and (v) these relationships are, however, not universal since the linear regression parameters (the slopes and the intercepts at the origin) depend on the system under investigation as well as on the nature of the excited state.

UR - http://www.scopus.com/inward/record.url?scp=34548462181&partnerID=8YFLogxK

U2 - 10.1063/1.2761886

DO - 10.1063/1.2761886

M3 - Article

AN - SCOPUS:34548462181

VL - 127

JO - The journal of chemical physics

JF - The journal of chemical physics

SN - 0021-9606

IS - 8

M1 - 084103

ER -