## Professor Takeshi Yanai

*Institute of Transformative Bio-Molecules, Nagoya University, Japan*

Multireference (MR) or multiconfigurational (MC) nature often need be considered for properly characterizing molecular electronic structures. It arises from, for example, excited state, transition-state geometries, or transition-metal complexes. The MR wavefunction cannot be accounted for by the single-determinant theory but with special computational approaches that can handle a superposition of multiple determinants to form a single state. In this lecture, the basics of the multireference or multiconfigurational quantum chemical methods will be overviewed, including techniques and algorithms for modeling of the higly-correlated many-electron wavefunctions.

### References:

(i) Helgaker, T., Jorgensen, P., & Olsen, J. (2014). Molecular electronic-structure theory. John Wiley & Sons.

(ii) T. Yanai, M. Saitow, X.-G. Xiong, Y. Kurashige, J. Chalupský, S. Guo, and S. Sharma, “Multi-state complete active-space second-order perturbation theory with density matrix renormalization group reference wave functions,” J. Chem. Theory Comput. 13 (10), pp 4829–4840 (2017).

(iii) T. Yanai, Y. Kurashige, W. Mizukami, J. Chalupský, T. N. Lan, and M. Saitow, “Density matrix renormalization group for ab initio Calculations and associated dynamic correlation methods: A review of theory and applications,” Int. J. Quantum Chem. 115, 283-299 (2015)