A5100399239- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- Advanced NMR Techniques and Applications
- Atmospheric Ozone and Climate
- Molecular spectroscopy and chirality
- Molecular Junctions and Nanostructures
- Spectroscopy and Laser Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Photoreceptor and optogenetics research
- Machine Learning in Materials Science
- Catalysis and Oxidation Reactions
- Electron Spin Resonance Studies
- Synthesis and Properties of Aromatic Compounds
- Ammonia Synthesis and Nitrogen Reduction
- Quantum, superfluid, helium dynamics
- Metalloenzymes and iron-sulfur proteins
- Atomic and Subatomic Physics Research
- Advanced Statistical Methods and Models
- Photosynthetic Processes and Mechanisms
- Advanced Fluorescence Microscopy Techniques
- Characterization and Applications of Magnetic Nanoparticles
- DNA and Nucleic Acid Chemistry
- Magnetism in coordination complexes
- Porphyrin and Phthalocyanine Chemistry
Seoul National University
2008-2025
California Institute of Technology
2020-2025
Korea Aerospace Research Institute
2012-2023
Pasadena City College
2020
Samsung (South Korea)
2012-2013
Handong Global University
2013
Yonsei University
2013
Nanyang Technological University
2013
Korea Aerospace University
2013
Yale University
2012
The idea to use quantum mechanical devices simulate other systems is commonly ascribed Feynman. Since the original suggestion, concrete proposals have appeared for simulating molecular and materials chemistry through computation, as a potential ``killer application''. Indications of exponential advantage in artificial tasks increased interest this application, thus, it critical understand basis chemistry. Here we gather evidence case most common task chemistry, namely, ground-state energy...
block2 is an open source framework to implement and perform density matrix renormalization group product state algorithms. Out-of-the-box it supports the eigenstate, time-dependent, response, finite-temperature In addition, carries special optimizations for ab initio electronic structure Hamiltonians implements many quantum chemistry extensions group, such as dynamical correlation theories. The code designed with emphasis on flexibility, extensibility, efficiency support integration external...
ConspectusWhile traditional quantum chemical theories have long been central to research, they encounter limitations when applied complex situations. Two of the most widely used approaches, Density Functional Theory (DFT) and Time-Dependent (TDDFT), perform well in cases with relatively weak electron correlation, such as ground-state minima closed-shell systems (Franck-Condon region). However, their applicability diminishes more demanding scenarios. These arise from reliance DFT on a...
We report on the findings of a blind challenge devoted to determining frozen-core, full configuration interaction (FCI) ground-state energy benzene molecule in standard correlation-consistent basis set double-ζ quality. As broad international endeavor, our suite wave function-based correlation methods collectively represents diverse view high-accuracy repertoire offered by modern electronic structure theory. In assessment, evaluated high-level are all found qualitatively agree final energy,...
The use of the mixed reference (MR) reduced density matrix, which combines matrices MS = +1 and -1 triplet-ground states, is proposed in context collinear spin-flip-time-dependent functional theory (SF-TDDFT) methodology. time-dependent Kohn-Sham equation with state solved by spinor-like open-shell orbitals within linear response formalism, enables to generate additional configurations realm TD-DFT. resulting MR-SF-TDDFT computational scheme has several advantages before conventional...
Due to their multiconfigurational nature featuring strong electron correlation, accurate description of diradicals and diradicaloids is a challenge for quantum chemical methods. The recently developed mixed-reference spin-flip (MRSF)-TDDFT method capable describing the electronic states these systems while avoiding spin-contamination pitfalls SF-TDDFT. Here, we apply MRSF-TDDFT study adiabatic singlet–triplet (ST) gaps in series well-known diradicaloids. On average, MRSF displays very high...
Analytic energy gradients of individual singlet and triplet states with respect to nuclear coordinates are derived implemented for the collinear mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT), which eliminates problematic spin-contamination SF-TDDFT. Dimensional-transformation matrices response spaces introduced, simplifying subsequent derivations. These enable general forms MRSF-TDDFT equations be similar those SF-TDDFT, suggesting that computational...
Non-radiative relaxation of the photoexcited thymine in gas phase shows an unusually long excited-state lifetime, and, over years, a number models, i.e., S1-trapping, S2-trapping, and S1&S2-trapping, have been put forward to explain its mechanism. Here, we investigate this mechanism using non-adiabatic molecular dynamics (NAMD) simulations connection with recently developed mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) method. We show that previously...
Excited-state aromatization dynamics in the photochemical ring opening of dihydroazulene (DHA) is investigated by nonadiabatic molecular simulations connection with mixed-reference spin-flip (MRSF)-TDDFT method. It found that, main reaction channel, occurs excited state a sequence steps increasing aromaticity. The first stage lasting ca. 200 fs produces an 8π semiaromatic S1 minimum (S1, min) through ultrafast damped bond length alternation (BLA) movement synchronized partial planarization...
Relativistic mixed-reference spin-flip (MRSF)-TDDFT is developed considering the spin–orbit coupling (SOC) within mean-field approximation. The resulting SOC-MRSF faithfully reproduces experiments with very high accuracy, which also consistent values by four-component (4c) relativistic CASSCF and 4c-CASPT2 in spin–orbit-energy splitting calculations of C, Si, Ge atoms. Even for fifth-row element Sn, yielded accurate splittings (∼ 3 % error). In SOC molecular 4-thiothymine a third-row...
Optimizing exchange–correlation functionals for both core/valence ionization potentials (cIPs/vIPs) and valence excitation energies (VEEs) at the same time in framework of MRSF-TDDFT is self-contradictory. To overcome challenge, within previous "adaptive exact exchange" or double-tuning strategy on Coulomb-attenuating XC (CAM), a new functional specifically cIPs vIPs was first developed by enhancing exchange to short- long-range regions. The resulting DTCAM-XI achieved remarkably high...
The mixed-reference spin–flip time-dependent density functional theory (MRSF-TD-DFT) method eliminates the erroneous spin contamination of SF-TD-DFT methodology, while retaining conceptual and practical simplicity latter. availability analytic gradient energy MRSF-TD-DFT response states enables automatic geometry optimization targeted states. Here, we apply new to optimize several S1/S0 conical intersections occurring in typical organic molecules. We demonstrate that is capable producing...
The mixed-reference spin-flip (MRSF) time-dependent density functional theory (TDDFT) method eliminates the notorious spin contamination of SF-TDDFT, thus enabling identification states proper spin-symmetry for automatic geometry optimization and molecular dynamics simulations. Here, we analyze optimize MRSF-TDDFT in calculations vertical excitation energies (VEEs) singlet–triplet (ST) gaps. dependence obtained VEEs ST gaps on intrinsic parameters is investigated, prescriptions use are...
We use MRSF-TDDFT and NEVPT2 methods to design singlet fission chromophores with the building blocks of cyclic (alkyl)(amino)carbenes (CAACs). CAAC dimers C2, C4, p-phenylene spacers are considered. The substitutions trifluoromethyls fluorine atoms at α C position investigated. electronegative substituents enhance π accepting capability while maintaining it as a quaternary atom. phenylene-connected two identified promising candidates for chromophores. cylindrically symmetric C2 C4 allow...
A new adaptive algorithm for penalty function optimization minimum-energy three-states conical intersections (ME3CI) is suggested. The differs from the original by (a) removing redundancy in target function, (b) using an increment weighting factor, and (c) tighter convergence criteria energy gap. latter was introduced to guarantee a true intersection rather than narrowly avoided crossing geometry. tested of ME3CI geometries butadiene malonaldehyde, where all previously found were recovered....
It is well-known that photolysis of pyrimidine nucleobases, such as uracil, in an aqueous environment results the formation hydrate one main products. Although several hypotheses regarding photohydration have been proposed past, e.g., zwitterionic and "hot" ground-state mechanisms, its detailed mechanism remains elusive. Here, theoretical nonadiabatic simulations uracil photodynamics reveal a highly energetic but kinetically stable intermediate features half-chair puckered ring strongly...
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A new mirror mounting technique applicable to the primary in a space telescope is presented. This replaces conventional bipod flexures with having mechanical shims so that adjustments can be made counter effects of gravitational distortion surface while being tested horizontal position. Astigmatic aberration due changes effectively reduced by adjusting shim thickness, and relation between astigmatism thickness investigated. We interferometrically at center curvature using null lens. Then we...
We used quantum chemistry methods at the levels of mixed-reference spin-flip time-dependent density functional theory and multireference perturbation to study diboron- diaza-doped anthracenes phenanthrenes. This class structures recently surged as potential singlet fission chromophores. studied electronic their excited states clarified reasons why they satisfy or fail energy criteria for Many have S1 not dominated by HOMO → LUMO excitation, so cannot be described using conventional two site...
We investigate the renormalized perturbative triples correction together with externally corrected coupled-cluster singles and doubles (ecCCSD) method. use density matrix renormalization group (DMRG) heat-bath CI (HCI) as external sources for ecCCSD equations. The accuracy is assessed potential energy surfaces of H2O, N2, F2. find that significantly improves upon ecCCSD, we do not see any instability respect to dissociation. explore how balance cost computing source amplitudes against...
We present a fast and accurate numerical algorithm for computing the first-order nonadiabatic coupling matrix element (NACME). The employs truncated Leibniz formula (TLF) approximation within finite-difference method, which makes it easily applicable in connection with any wave function-based methodology. In this work, we used recently developed mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT, MRSF brevity). accuracy is assessed NACME between singlet electronic...
The molecular orbital (MO) concept is a useful tool, which relates the ground-state energy with energies (and occupations) of individual orbitals. However, analysis excited states from linear response computations performed in terms initial state MOs or some other forms orbitals, e.g., natural transition Because these orbitals lack respective energies, they do not allow developing consistent picture states. Herein, we argue that Dyson's enable description compatible concepts theory. Dyson...
The effect of the existence several prototropic tautomers cytosine on its UV/vis spectra and excited state decay dynamics is studied by spectral nonadiabatic molecular (NAMD) simulations in connection with mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) method. Simulated provide a strong indication that H3N keto–amino tautomer (the least anticipated species) may be present under experimental conditions. NAMD yield wide range constants for various cytosine,...
It is demonstrated that significant accuracy improvements in MRSF-TDDFT can be achieved by introducing two different exchange–correlation (XC) functionals for the reference Kohn–Sham DFT and response part of calculations, respectively. Accordingly, new XC doubly tuned Coulomb attenuated method-vertical excitation energy (DTCAM-VEE) DTCAM-AEE were developed on basis "adaptive exact exchange (AEE)" concept framework Coulomb-attenuating functionals. The values DTCAM-VEE are excellent agreement...