Laplace-Transform GW

We present a simple and accurate GW implementation based on a combination of a Laplace transformation (LT) and other acceleration techniques used in post-SCF quantum chemistry, namely, natural auxiliary functions and the frozen-core approximation. The LT-GW approach combines three major benefits: (a) a small prefactor for the computational scaling, (b) easy integration into existing molecular GW implementations, and (c) significant performance improvements for a wide range of possible applications. Illustrating these advantages for systems consisting of up to 352 atoms and 7412 basis functions, we further demonstrate the benefits of this approach combined with an efficient implementation of the Bethe-Salpeter equation

Electronic couplings for photo-induced processes from subsystem time-dependent density-functional theory: The role of the diabatization

Subsystem time-dependent density-functional theory (sTDDFT) making use of approximate non-additive kinetic energy (NAKE) functionals is known to be capable of describing excitation energy transfer processes in a variety of applications. Here, we show that sTDDFT, especially when combined with projection-based embedding (PbE), can be employed for the entire range of photo-induced electronic couplings essential for modeling photophysical properties of complex chemical and biological systems and therefore represents a complete toolbox for this class of problems. This means that it is capable of capturing the interaction/coupling associated with local- and charge-transfer (CT) excitons. However, this requires the choice of a reasonable diabatic basis. We therefore propose different diabatization strategies of the virtual orbital space in PbE-sTDDFT and show how CT excitations can be included in sTDDFT using NAKE functionals via a phenomenological approach. Finally, these electronic couplings are compared to couplings from a multistate fragment excitation difference (FED)–fragment charge difference (FCD) diabatization procedure. We show that both procedures, multistate FED–FCD and sTDDFT (with the right diabatization procedure chosen), lead to an overall good agreement for the electronic couplings, despite differences in their general diabatization strategy. We conclude that the entire range of photo-induced electronic couplings can be obtained using sTDDFT (with the right diabatization procedure chosen) in a black-box manner

Triplet Excitation-Energy Transfer Couplings from Subsystem Time-Dependent Density-Functional Theory

We present an implementation of Triplet Excitation-Energy Transfer (TEET) couplings based on subsystem-based Time-Dependent Density-Functional Theory (sTDDFT). TEET couplings are systematically investigated by comparing "exact" and approximate variants of sTDDFT. We demonstrate that, while sTDDFT utilizing explicit approximate Non-Additive Kinetic Energy (NAKE) density functionals is well-suited for describing Singlet Excitation-Energy Transfer (SEET) processes, it is inadequate for characterizing TEET. However, we show that Projection-based Embedding (PbE)-based sTDDFT addresses the challenges faced by NAKE-sTDDFT and emerges as a promising method for accurately describing electronic couplings in TEET processes. We also introduce the mixed PbE-/NAKE-embedding procedure to investigate TEET effects in solvated pairs of chromophores. This approach offers a good balance between accuracy and efficiency, enabling comprehensive studies of TEET processes in complex environments

Exact relationships between the GW approximation and equation-of-motion coupled-cluster theories through the quasi-boson formalism

We describe the relationship between the GW approximation and various equation-of-motion (EOM) coupled-cluster (CC) theories. We demonstrate the exact equivalence of the G$_0$W$_0$ approximation and the propagator theory for an electron-boson problem in a particular excitation basis. From there, we establish equivalence within the quasi-boson picture to the IP+EA-EOM unitary coupled-cluster propagator. We analyze the incomplete description of screening provided by the standard similarity-transformed IP+EA-EOM-CC and the recently introduced G$_0$W$_0$ Tamm-Dancoff approximation. We further consider the approximate decoupling of IP and EA sectors in EOM-CC treatments and devise the analogous particle-hole decoupling approach for the G$_0$W$_0$ approximation. Finally, we numerically demonstrate the exact relationships and magnitude of the approximations in calculations of a set of molecular ionization potentials and electron affinities

AB-G0_0W0_0: A practical G0_0W0_0 method without frequency integration based on an auxiliary boson expansion

Common G$_0$W$_0$ implementations rely on numerical or analytical frequency integration to determine the G$_0$W$_0$ self-energy, which results in a variety of practical complications. Recently, we demonstrated an exact connection between the G$_0$W$_0$ approximation and equation-of-motion (EOM) quantum chemistry approaches [J. Chem. Phys., 158, 124123 (2023)]. Based on this connection, we propose a new method to determine G$_0$W$_0$ quasiparticle energies which completely avoids frequency integration and its associated problems. To achieve this, we make use of an auxiliary boson (AB) expansion. We name the new approach AB-G$_0$W$_0$ and demonstrate its practical applicability in a range of molecular problems

Toll-like Rezeptor 3 vermittelte Pluripotenz gingivaler mesenchymaler Stammzellen

Die Parodontitis ist eine lokal entzündliche Erkrankung mit progressivem Verlauf bis hin zum vollständigen Abbau parodontalen Attachments. Mit einer Morbidität von 95% aller bezahnten Menschen stellt die Parodontitis eine der häufigsten Erkrankungen weltweit dar, sodass der Behandlung und Regeneration des verlorenen Knochens größte Bedeutung zukommt. Parodontale Stammzellen sind der Ausgangspunkt der lokalen zellulären Regeneration. Prominente Vertreter dieser Gruppe sind die gingivalen mesenchymalen Stammzellen (G-MSCs), welche eine einfach zugängliche Stammzellreserve im adulten Organismus bilden. Sie bewiesen in vivo und in vitro bemerkenswerte pluripotente Eigenschaften in Form der Selbsterneuerung und Differenzierbarkeit in multiple Zellentitäten wie Knochen-, Fett- und Knorpelgewebe. Des Weiteren konnten diverse Mustererkennungsrezeptoren in und an den Zellen nachgewiesen werden. Ein prominenter Vertreter dieser Rezeptoren ist Toll-like Rezeptor 3 (TLR3), der intrazellulär/endosomal gelegen durch virale dsRNA aktiviert wird. TLR3 greift über verschiedene Signalwege (Wnt/β-Catenin, NF-κB, IRF3/7) in die Genexpression der Zelle sowie die Expression inflammativer Zytokine ein. Ziel dieser Studie war es, den Einfluss der Aktivierung von TLR3 mittels des dsRNA Analogon Poly(I:C) HMW auf die pluripotenten Charakteristika der G-MSCs zu untersuchen. Zu diesem Zweck wurde Mischgewebe aus Gingivaexzisaten (n=5) gesunder Patienten kultiviert und G-MSCs via immunomagnetischer Säulenseparation über den Stro-1 Rezeptor isoliert. Nach Charakterisierung gemäß den Richtlinien der International Society for Cellular Therapy (ISCT) und Nachweis der Expression von TLR3 wurden die Kulturen mit Poly(I:C) stimuliert und in Genexpression (RT-qPCR), Phänotyp (Durchflusszytometrie), Zellaktivität (MTT), Koloniebildung (CFU), Proliferation und multilinearer Differenzierung verglichen. Die Aktivierung von TLR3 führte nach 24h zu einer vermehrten Expression von CD73, CD90, CD105 und CD146 sowie höherer metabolische Aktivität und REX-1 Expression. Die Transkripte für NANOG, OCT4A, SOX2, MSX-1 und KLF4 wurden hingegen vermindert und auch CD34 verstärkt exprimiert. CFU und Proliferation waren über 12 Tage vermindert, genau wie die MTT an Tag 6 und 12. Die osteo-/ chondrogenen Differenzierungslinien wurden verstärkt. Wir schließen aus den Erkenntnissen, dass Poly(I:C) initial einen steigernden Einfluss auf die Pluripotenz besitzt, dieser Effekt verschwindet jedoch schnell zugunsten eines starken Differenzierungsimpulses, der besonders die Differenzierung in osteo-chondraler Direktion fördert. Die gewonnenen Erkenntnisse bieten uns einen weiterführenden Einblick in die immunomodulatorischen Verknüpfungen gingivaler Stammzellen und die enge Vergesellschaftung des Mikroenvironments mit dem zellulären regenerativen Potential lokaler Stammzellpopulationen. Langfristig könnte es möglich sein, diese Erkenntnisse zu nutzen, um die parodontale Regeneration durch exogene oder endogene Stimuli zu verstärken und den Gewebeumsatz zugunsten der Regeneration präventiv zu erhöhen

Ab initio quantum many-body description of superconducting trends in the cuprates

Using a systematic ab initio quantum many-body approach that goes beyond low-energy models, we directly compute the superconducting pairing order of several doped cuprate materials and structures. We find that we can correctly capture two well-known trends: the pressure effect, where pairing order increases with intra-layer pressure, and the layer effect, where the pairing order varies with the number of copper-oxygen layers. From these calculations, we observe that the strength of superexchange and the covalency at optimal doping are the best descriptors of the maximal pairing order. Our microscopic analysis further identifies short-range copper spin fluctuations, together with multi-orbital charge fluctuations, as central to the pairing trends. Our work illustrates the possibility of a quantitative computational understanding of high-temperature superconducting materials.Comment: 10 pages, 5 figures, with supplementary material

Block2: a comprehensive open source framework to develop and apply state-of-the-art DMRG algorithms in electronic structure and beyond

Block2 is an open source framework to implement and perform density matrix renormalization group and matrix product state algorithms. Out-of-the-box it supports the eigenstate, time-dependent, response, and finite-temperature algorithms. In addition, it carries special optimizations for ab initio electronic structure Hamiltonians and implements many quantum chemistry extensions to the density matrix renormalization group, such as dynamical correlation theories. The code is designed with an emphasis on flexibility, extensibility, and efficiency, and to support integration with external numerical packages. Here we explain the design principles and currently supported features and present numerical examples in a range of applications.Comment: 20 pages, 8 figure

Thymoquinone-Mediated Modulation of Toll-like Receptors and Pluripotency Factors in Gingival Mesenchymal Stem/Progenitor Cells

Thymoquinone (TQ), the key active component of Nigella sativa (NS), demonstrates very promising biomedical anti-inflammatory, antioxidant, antimicrobial and anticancer properties. Several investigations have inspected the modulative activities of TQ on different stem/progenitor cell types, but its possible role in the regulation of gingival mesenchymal stem/progenitor cells (G-MSCs) has not yet been characterized. For the first time, this study investigates the effects of TQ on G-MSCs’ stemness and Toll-like receptor expression profiles. G-MSCs (n = 5) were isolated, sorted via anti-STRO-1 antibodies and then disseminated on cell culture dishes to create colony-forming units (CFUs), and their stem/progenitor cell attributes were characterized. TQ stimulation of the G-MSCs was performed, followed by an examination of the expression of pluripotency-related factors using RT-PCR and the expression profiles of TLRs 1–10 using flowcytometry, and they were compared to a non-stimulated control group. The G-MSCs presented all the predefined stem/progenitor cells’ features. The TQ-activated G-MSCs displayed significantly higher expressions of TLR3 and NANOG with a significantly reduced expression of TLR1 (p < 0.05, Wilcoxon signed-rank test). TQ-mediated stimulation preserves G-MSCs’ pluripotency and facilitates a cellular shift into an immunocompetent-differentiating phenotype through increased TLR3 expression. This characteristic modulation might impact the potential therapeutic applications of G-MSCs