First-principles $\mathit{GW}$ calculations for DNA and RNA nucleobases

On the basis of first-principles GW calculations, we study the quasiparticle properties of the guanine, adenine, cytosine, thymine, and uracil DNA and RNA nucleobases. Beyond standard $G_0{W}_0$ calculations, starting from Kohn-Sham eigenstates obtained with (semi)local functionals, a simple self-consistency on the eigenvalues allows us to obtain vertical ionization energies and electron affinities within an average 0.11 and 0.18 eV error, respectively, as compared to state-of-the-art coupled-cluster and multiconfigurational perturbative quantum chemistry approaches. Further, GW calculations predict the correct $\pi$-character of the highest occupied state, due to several level crossings between density functional and GW calculations. Our study is based on a recent Gaussian-basis implementation of GW calculations with explicit treatment of dynamical screening through contour deformation techniques.

Figure 1

Schematic representation of the molecular structure of (a) guanine (G9K), (b) adenine, (c) cytosine (C1), (d) thymine, and (e) uracil. Black, brown, red, and white atoms are carbon, nitrogen, oxygen, and hydrogen, respectively. The G9K and C1 notations for the guanine and cytosine tautomers are consistent with Ref. 6.

Figure 2

Ionization energies in eV. The vertical (maroon) error bars indicate the experimental range. Triangles (light blue): LDA values; (green) squares: $G_0{W}_0(\mathrm{LDA})$ values; solid black diamond: GW values; (red) empty circles (QuantChem abbreviation): quantum chemistry, namely, CCSD(T), CASPT2, and EOM-IP-CCSD, values (see text).

Figure 3

Isodensity surface plot of the HOMO (${\sigma }_O$), HOMO-1 ($\pi$), HOMO-2 ($\sigma$), and HOMO-3 (${\pi }^{\prime }$) LDA Kohn-Sham eigenstates of cytosine. Within GW, the ordering of states becomes $\pi$, ${\pi }^{\prime }$, ${\sigma }_O$, $\sigma$ for HOMO to HOMO-3 (see text).