All-electron GW plus Bethe-Salpeter calculations on small molecules

作者：Hirose Daichi^*; Noguchi Yoshifumi; Sugino Osamu

来源：Physical Review B, 2015, 91(20): 205111.

DOI：10.1103/PhysRevB.91.205111

Accuracy of the first-principles GW+Bethe-Salpeter equation (BSE) method is examined for low-energy excited states of small molecules. The standard formalism, which is based on the one-shot GW approximation and the Tamm-Dancoff approximation (TDA), is found to underestimate the optical gap of N-2, CO, H2O, C2H4, and CH2O by about 1 eV. Possible origins are investigated separately for the effect of TDA and for the approximate schemes of the self-energy operator, which are known to cause overbinding of the electron-hole pair and overscreening of the interaction. By applying the known correction formula, we find the amount of the correction is too small to overcome the underestimated excitation energy. This result indicates a need for fundamental revision of the GW+BSE method rather than adjustment of the standard one. We expect that this study makes the problems in the current GW+BSE formalism clearer and provides useful information for further intrinsic development beyond the current framework.

• 出版日期2015-5-13