Kohn–Sham energy decomposition for molecules in a magnetic field

Abstract

I joined the Oslo group of theoretical chemistry in my last semester as a bachelor student. Then, I got my master's degree with Trygve Helgaker and Erik Tellgren as my supervisors, and now, finally, my Ph.D. As such, I've been a part of this excellent community for nine years. I've seen the Centre of Theoretical and Computational Chemistry end, and I've seen the Hylleraas Centre of Quantum Molecular Sciences rise. Naming all the generous, kind and interesting people I've interacted with over the years is impossible, but I'll mention a few.My supervisors, Trygve and Erik, have guided me through this project and have granted me more encouragement and patience than I could possibly deserve. Alex Borgoo also acted as unofficial supervisor for a time, and helped me get back on track when things looked bleak. To Glenn B.S. Miller, who started studying chemistry at the same semester as I, and who defended his Ph.D years before me: Thank you for a lasting friendship -and for your linguistic feedback! To Patrick, Volodja, Kai, Chamdan, John, Jostein, Sigbjørn, Julie, Llouis, and all the other temporary inmates of our little office: I will never forget the general atmosphere you created, how helpful you all were, and how enjoyable it has been to be your colleague. So long, and thanks for all the fish! Also a great thank you to Henrik Austad and Vidar Løkken for your indispensable advice on programming, operating systems, backup routines and all the CPU time you have generously granted me on your personal servers. I assure you, there are few privately owned servers out there that have done more number crunching on quantum mechanical systems in magnetic fields.However, there is one person in particular who deserves more credit and praise than anyone else: My wife, Marianne. Being a struggling scientist is hard on the environment in general and on the family in particular. When I was disorganized, she helped me retrieve the loose ends. When I despaired, she encouraged. When I sacrificed all my duties at home and with the family to concentrate on my work, she covered for me. Without her, this would project would be nothing but a dead dream. That is a debt I can never repay. From the bottom of my heart: Thank you! i ii List of Articles I. Kohn-Sham energy decomposition for molecules in a magnetic field, published in Molecular Physics [1].II. Bonding in strong magnetic fields: role of spin and angular momentum, submitted for publication.III. Effects of strong magnetic fields on water from rigorous quantum calculations, to be submitted for publication.iii iv

Modeling Ultrafast Electron Dynamics in Strong Magnetic Fields Using Real-Time Time-Dependent Electronic Structure Methods

“…In general, when an external magnetic field is applied to a molecule, the energy may either decrease paramagnetically or increase diamagnetically. Paramagnetism is often (though not always 73 ) associated with open-shell molecules, whilst diamagnetism is associated with closed-shells. The electronic Hamiltonian in the presence of a uniform magnetic field B is …”

“…This in turn enables the calculation of excitation energies rigorously at the meta-GGA level in line with ref ( 52 ) at zero field and seamlessly for magnetic fields of arbitrary strengths. Our previous work has demonstrated that, in such strong magnetic fields, the use of meta-GGA functionals including current-dependent terms can deliver much improved accuracy compared with LDA and GGA type functionals 47 , 73 and so provide a good starting point for the determination of excitation energies in strong magnetic fields.…”

Benchmarking density functional approximations for diamagnetic and paramagnetic molecules in nonuniform magnetic fields

“…Basis set convergence of the anapole susceptibility values was well-studied and MODENA basis sets were proposed to be superior to Dunning's basis sets. Previous studies of density functional approximations for magnetic properties like magnetizabilities and NMR shielding constants 12,35,36 have indicated that meta-GGA functionals, in particular cTPSS, are promising candidates for capturing even exotic magnetic effects very far from the domain these functionals were explicitly constructed for. Remarkably, it was also found that the errors for the paramagnetic closed shell molecules were an order of magnitude higher for all the methods studied except for cTPSS (current TPSS).…”

Density Functional Theories and Coordination Chemistry

“…Other more specific tools based on the fractional occupation number weighted density, 194 electron localization functions (ELF) 195 or KS energy decomposition 196 have been developed for a qualitative analysis of complicated electronic structure solutions.…”