<h3>Title</h3>
<p><span style="color: #0000ff;">Dynamic Electron Correlation with Adiabatic Connection Approaches: describing excited states and molecular interactions</span></p>
<p><strong><span style="text-decoration: underline;">Abstract</span> :</strong></p>
<p style="text-align: justify;">Correlation energy, despite being a small fraction of the total electronic energy, governs binding of atoms into molecules. Similarly, noncovalent molecular interactions are flawed if the correlation of electrons belonging to interacting subsystems is not accounted for. The two main approaches to electron-correlation involve either perturbation theory or are based on density functionals. They are deficient either in accuracy or computational efficiency and a generally applicable, computationally efficient approach remains a challenge.</p>
<p style="text-align: justify;">Recently we have proposed a novel approach to describing electron correlation in multireference systems by adopting the adiabatic connection (AC) formalism [1]. The latter naturally links electron correlation with fluctuation of density at different points in space. Consequently, the final expression for the correlation energy employs density linear response. In our formalism, we use extended random phase approximation (ERPA) to describe the latter. The proposed AC-ERPA method yields excellent results for ground and excited states of molecules described with the CASSCF wavefunction [2-4]. In my talk I will present applications of the AC methods, and their extensions to multiconfigurational DFT [5], to challenging multireference systems and noncovalently bounded excited state systems.</p>
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<p>References</p>
<p>1. K. Pernal, Phys. Rev. Lett. 120 (2018), 013001.</p>
<p>2. E. Pastorczak, K. Pernal, J. Chem. Theory Comput. 14 (2018), 3493.</p>
<p>3. E. Pastorczak, K. Pernal, J. Phys. Chem. Lett. 9 (2018), 5534.</p>
<p>4. E. Pastorczak, M. Hapka, L. Veis, and K. Pernal, J. Phys. Chem. Lett. 10 (2019), 4668.</p>
<p>5. M. Hapka, E. Pastorczak, A. Krzeminska, and K. Pernal, J. Chem. Phys. 152 (2020), 094102</p>