New Videos from the Wormit Award Webinar Mini-Symposium

Watch the videos from our 2020 Wormit Award virtual event presented on December 2, 2020:

• "From single-molecule magnets to infinite spin chains: A many-body adventure" presented by Dr. Pavel Pokhilko (University of Michigan);
• "Electronic structure methods based on absolutely localized molecular orbitals: from non-covalent interactions to electron transfer" presented by Dr. Yuezhi Mao (Stanford University).

The entire Wormit Award Mini-Symposium can be viewed on the Q-Chem YouTube page.

Held to honor our two 2020 Wormit Award winners, our mini-symposium / webinar was held on December 2, 2020.  Our 2020 winners, Pavel Pokhilko and Yuezhi Mao, each gave a short talk followed by a Q&A session. 

ABSTRACTS:

"From single-molecule magnets to infinite spin chains: A many-body adventure"

Single-molecule magnets are molecules with one or several radical centers, showing magnetic properties. They can serve as building blocks of extended magnetic or ferroelectric materials. Their theoretical treatment is challenging because one needs to tackle both strong and weak correlations and also include relativistic effects, such as spin-orbit interaction. I will describe new tools that we developed for the rigorous and quantitative treatment of magnetic systems. Our approach is grounded in the equation-of-motion coupled-cluster (EOM-CC) theory. We treat spin-orbit interactions in an ansatz-agnostic fashion, using reduced quantities, such as one-particle density matrices, and the Wigner-Eckart theorem. To access larger systems, we use the effective Hamiltonian approach. The effective Hamiltonians, derived from EOM-CC wavefunctions by means of Bloch theory, enable extrapolation of properties computed for finite systems to the infinite number of spins. In my talk, I will illustrate this approach by a few examples including iron-based SMMs and copper oxalate.

"Electronic structure methods based on absolutely localized molecular orbitals: from non-covalent interactions to electron transfer"

Abstract

Absolutely localized molecular orbitals (ALMOs) offer a way to construct electronic states with charge localized on molecular fragments. In this seminar, I will introduce the development of electronic structure methods using ALMOs for two distinct objectives. The first is to characterize non-covalent interactions both qualitatively and quantitively, for which we developed the ALMO-based energy decomposition analysis (ALMO-EDA), a scheme that is able to partition monolithic total interaction energy into physically meaningful, intuitive terms, such as electrostatics, dispersion, etc. I will highlight the recent extension of ALMO-EDA to treat non-covalent interactions in solvation environments, as well as the formulation and application of the “adiabatic” ALMO-EDA that extends the capacity of this method to decompose not only interaction energies but also molecular property shifts arising from intermolecular binding. The second objective is to construct chemically intuitive diabatic states for the study of thermal and photoinduced electron transfer. We obtain variationally optimized charge-localized diabats from density functional theory (DFT) calculations using ALMOs and have developed a modified multistate DFT scheme to accurately predict the electronic couplings between ALMO-based diabats. This approach shows superior accuracy over many other commonly used DFT-based diabatization methods over a broad array of ground-state electron and hole transfer problems. I will then show how one can extend this method to accurately predict diabatic couplings that govern photoinduced electron transfer, by combing the ∆SCF technique with ALMO-based DFT calculations.