Structural Control Research Articles

Enhancing Building Stability and Seismic Resilience with Water-Added Tuned Mass Dampers

These days, the construction industry is increasingly producing buildings with extremely low damping values. Under structural vibrations caused by storms and earthquakes, structures can collapse easily. There are now several methods for reducing structural vibrations, and one of the methods currently employed is the Tuned Mass Damper (TMD). Research is being conducted to determine its performance and importance. The entire damper was tuned for various constructions. An eight-story model specifically designed for the structure was used in this study to observe the structure's response with and without TMD during shaking table experiments. Compared to passive control devices (PTMDs), Active Tuned Mass Dampers (ATMDs) are more efficient as they are active control devices powered externally. By maintaining the structure's frequency, damping, and stiffness constant, other variables such as the percentage reduction in structural capacity can effectively control structure vibrations. The findings and observations from TMD studies can be used to address challenges in earthquake structural control considering current technological limitations and energy demands. The results illustrate significant improvements with damping: the damped structure experienced a 21% increase in acceleration, a 17% increase in velocity, and a 79% reduction in displacement compared to the un damped structure. These findings underscore the effectiveness of damping in mitigating earthquake-induced vibrations.

Morphology evolution and mechanism of massive three-level hierarchically porous silver fabricated by vapor phase dealloying

In this study, the Gasar process and vapor phase dealloying (VPD) method were combined to fabricate a massive three-level hierarchical porous silver (MTHPS), which composed of interconnected micron-sized, submicron-sized, and nanoporous structures. The key aspect of this study lies in the preparation of a hypoeutectic Gasar Mg91.6Ag8.4 alloy with the regular micron-scale pore structure as the dealloying precursor, improving the size of the hierarchical porous metal. Under high vacuum conditions, by adjusting the dealloying time and temperature, MTHPS samples with various morphologies were obtained. After dealloying, the MTHPS exhibited Gasar pores (diameter 376 ± 86 μm), submicron pores (diameter 465 ± 125 nm), and a continuous ligament/channel structure (pore size less than 70 ± 40 nm). The coarsening index was 3.6258, and the activation energy was measured to be 0.95 eV, indicating that the formation and coarsening of the pores during VPD are attributed to surface diffusion. The calculated evaporated mass of the precursor alloy after dealloying was very close to the experimental value (±0.004 g), indicating that the evaporation of Mg occurred simultaneously in both solid and liquid phases during the VPD process. This study elucidates the phase transformation characteristics, structural control, and diffusion mechanisms of MTHPS prepared by VPD, providing valuable insights for further research and applications of MTHPS.

Enhancement of peroxymonosulfate activation through regulating electronic structure of cobalt phthalocyanine by g-C3N4 for rhodamine B degradation

The catalytic performance of cobalt-based catalysts in Fenton-like reactions is significantly influenced by the electron density of Co centers. However, precise control of the electronic structure to enhance the degradation activity remains a challenge. This paper demonstrates a method to enhance the catalytic activity of cobalt phthalocyanine (CoPc) by modulating its electronic structure via integrating with graphitic carbon nitride (g-C3N4). The electron redistribution between g-C3N4 and CoPc was observed, resulting in electron-rich Co centers. Consequently, the CoPc/g-C3N4 composites exhibit significantly enhanced peroxymonosulfate (PMS) activation capability compared to CoPc and their physical mixtures. The improved catalytic performance is due to the electron-rich Co centers, better dispersion of CoPc, and enhanced hydrophilicity. This study proposes a novel strategy for the design of efficient PMS activation catalysts.

Robust active vibration control of flexible smart beam by μ-synthesis

This paper presents a comprehensive method for designing a robust active vibration control system to suppress low-frequency vibrations in smart structures. A novel finite element method based on the first-order shear deformation theory is used to calculate the dynamic response of a smart beam. Through a comprehensive system identification process, the uncertain model of the smart beam is extracted considering both the magnitude and phase. The model fits the experimental data successfully. In addition, a generalized low-frequency vibration control performance function is designed for the piezoelectric smart beam. Using a linear fractional transformation, the system is converted into a standard μ-synthesis control framework, and the controller K is synthesized using structural singular values μ. The effectiveness of the proposed method is experimentally validated using a setup with a piezoelectric smart beam. The experimental results suggest that the proposed control method exhibits robust stability and robust performance, effectively enhancing the performance of smart structure control in various scenarios. The proposed control framework utilizes structured singular value analysis to provide optimal robust stability margins and superior robust control performance, effectively addressing system uncertainties and non-linearities.

Structural controls on hydrothermal fluid flow in a carbonate geothermal reservoir: Insights from giant carbonate veins in western Germany

This study examines the impact of polyphase tectonics on the development of structurally controlled hydrothermal fluid pathways in carbonate geothermal reservoirs. Our case study focuses on hydrothermal carbonate veins and vein-filled faults in Devonian carbonates from the North Rhine-Westphalia region in western Germany, currently being explored as a potential low-enthalpy geothermal reservoir at depths of 4–5 km. These veins, which can be up to 20 m thick, are subvertical and strike NNW, N, or ESE. They exhibit pinch-and-swell undulating geometries, faulted vein-wall contacts, and occasional fillings of hydrothermal breccias. Vein-filled normal faults show hybrid shear-dilatant openings, with fault tips characterized by horsetail vein terminations. The textures, orientations, and age of the veins suggest their formation at low confining pressures and at depths < 2 km during the Post-Variscan East-West extension. Orthogonal North- and East-striking strike slip faults, inherited from the Variscan orogeny, were likely reactivated during post-Variscan extension, with a significant dilatant component that formed the observed veins. In the Ruhr Basin, the dilation tendency analysis indicates that NNW-striking veins or joints are optimally oriented for re-opening under the current strike-slip stress regime, characterized by NNW-trending maximum horizontal stress. The intersections of fractures may currently create moderately SSE-plunging linear zones of enhanced fluid flow. The main uncertainty regards the presence of similar structures at geothermal reservoir depths of ∼4–5 km in the Middle Devonian carbonates underneath the Ruhr Basin. As the study veins are likely to have formed at depths <2 km, the existence of analogous dilatant conduits at greater depths remains speculative. Eventually, we propose that zones characterized by open discontinuities and channelized fluid flow in carbonate geothermal reservoir in strike-slip tectonic settings can be: (a) dilational jogs between overlapping strike-slip faults, (b) bends along faults, and (c) strike-slip fault terminations with horsetail extensional structures. These zones can also be prone to enhanced karstification.

Wavy Graphene Nanoribbons Containing Periodic Eight‐Membered Rings for Light‐Emitting Electrochemical Cells

Precision graphene nanoribbons (GNRs) offer distinctive physicochemical properties that are highly dependent on their geometric topologies, thereby holding great potential for applications in carbon‐based optoelectronics and spintronics. While the edge structure and width control has been a popular strategy for engineering the optoelectronic properties of GNRs, non‐hexagonal‐ring‐containing GNRs remain underexplored due to synthetic challenges, despite offering an equally high potential for tailored properties. Herein, we report the synthesis of a wavy GNR (wGNR) embedding periodic eight‐membered rings into its carbon skeleton, which is achieved by the A2B2‐type Diels‐Alder polymerization between dibenzocyclooctadiyne (6) and dicyclopenta[e,l]pyrene‐5,11‐dione derivative (8), followed by a selective Scholl reaction of the obtained ladder‐type polymer (LTP) precursor. The obtained wGNR, with a length of up to 30 nm, is thoroughly characterized by solid‐state NMR, FT‐IR, Raman, and UV‐Vis spectroscopy with the support of DFT calculations. The non‐planar geometry of wGNR efficiently prevents the inter‐ribbon π‐π aggregation, leading to photoluminescence in solution. Consequently, the wGNR can function as an emissive layer for organic light‐emitting electrochemical cells (OLECs), offering a proof‐of‐concept exploration in implementing luminescent GNRs into optoelectronic devices. The fast‐responding OLECs employing wGNR will pave the way for advancements in OLEC technology and other optoelectronic devices.

Wavy Graphene Nanoribbons Containing Periodic Eight-Membered Rings for Light-Emitting Electrochemical Cells.

Precision graphene nanoribbons (GNRs) offer distinctive physicochemical properties that are highly dependent on their geometric topologies, thereby holding great potential for applications in carbon-based optoelectronics and spintronics. While the edge structure and width control has been a popular strategy for engineering the optoelectronic properties of GNRs, non-hexagonal-ring-containing GNRs remain underexplored due to synthetic challenges, despite offering an equally high potential for tailored properties. Herein, we report the synthesis of a wavy GNR (wGNR) embedding periodic eight-membered rings into its carbon skeleton, which is achieved by the A2B2-type Diels-Alder polymerization between dibenzocyclooctadiyne (6) and dicyclopenta[e,l]pyrene-5,11-dione derivative (8), followed by a selective Scholl reaction of the obtained ladder-type polymer (LTP) precursor. The obtained wGNR, with a length of up to 30 nm, is thoroughly characterized by solid-state NMR, FT-IR, Raman, and UV-Vis spectroscopy with the support of DFT calculations. The non-planar geometry of wGNR efficiently prevents the inter-ribbon π-π aggregation, leading to photoluminescence in solution. Consequently, the wGNR can function as an emissive layer for organic light-emitting electrochemical cells (OLECs), offering a proof-of-concept exploration in implementing luminescent GNRs into optoelectronic devices. The fast-responding OLECs employing wGNR will pave the way for advancements in OLEC technology and other optoelectronic devices.

Design and performance evaluation of toroidal TLCDs in bidirectional seismic control of structures using a modified dynamic model

In this study, a modified dynamic model which distinguishes between liquid oscillation and sloshing in vertical columns is derived for toroidal tuned liquid column dampers (TLCDs). In the modified model of toroidal TLCDs, the primary sloshing mode within vertical columns is modeled as mass–spring-dashpot systems, whereas the oscillatory behavior of the liquid is analyzed employing the conventional theory of TLCDs. The accuracy of the modified dynamic model in capturing bidirectional liquid responses is verified by computational fluid dynamics (CFD)-based simulations. A large number of CFD-based simulations are performed to establish a ready-to-use suggested formula for a newly introduced parameter (which is related to the geometric configuration of liquid containers and the initial liquid depth) in the modified model. Subsequently, considering the maximum allowable liquid displacement in vertical columns, an optimized design approach for toroidal TLCDs installed in symmetric and asymmetric structures is illustrated. On the basis of the proposed optimization design method, the bidirectional vibration control effects of toroidal TLCDs are comprehensively analyzed under El Centro, Loma Prieta, Northridge, and Chi–Chi seismic excitations in both the time and frequency domains. The results demonstrate the effectiveness of toroidal TLCDs for bidirectional seismic control of structures.

The Structure Control of MoC Optimizes Charge Transfer to Improve Solar Cell Performance

The Structure Control of MoC Optimizes Charge Transfer to Improve Solar Cell Performance

Discrete-Time Sliding Mode Control Strategies—State of the Art

Variable structure control systems are known to provide a high level of robustness to external disturbances and modeling uncertainties with comparably low computational complexity. Thanks to these features, they have found applications in various fields, such as power engineering, electronics, robotics, and aviation. In recent decades, the field of sliding mode control has developed significantly. Therefore, this study aims to discuss the basic concepts and design methodology of such strategies. Although in the 20th century, continuous-time sliding mode control has been the center of the control engineering society’s attention, it has certain major shortcomings. In particular, such control schemes result in undesirable high-frequency oscillations when applied digitally. Therefore, the more recent discrete-time approach to sliding mode control has gained recognition in the 21st century. Since the introduction of discrete-time sliding mode control strategies, the reaching law-based controller design method has been designed, within which two main paradigms may be named: the switching type and the nonswitching type quasi-sliding mode. This paper presents a broad review of the discrete-time sliding mode control strategies, starting from the definition of sliding mode through the controller design procedures and up to potential applications. The aim of this study is to provide an up-to-date state of the art and introduce readers to the newest trends and achievements in the field of sliding mode control.

Achieving high strength and ductility in Inconel 718: tailoring grain structure through micron-sized carbide additives in PBF-LB/M additive manufacturing

ABSTRACT Few attempts have been made so far to develop modifiers for in situ use in Inconel 718 PBF-LB/M fabrication. Reports show an increase in tensile strength compared to unmodified counterparts. However, significant ductility reduction is observed, outweighing the mere tensile strength improvements when considering practical applications. In this study, micron-sized powder modifiers (NbC, TiC, and B4C) were added in proportions of 0.6 wt.% (NbC and TiC) and 0.2 wt.% (B4C) to Inconel 718 powder for PBF-LB/M processing. These modifiers allowed for grain structure control during heat treatment, including hot isostatic pressing. The addition of NbC resulted in a finer grain structure, while the addition of TiC preserved the as-built grain structure after heat treatment. Carbide precipitates led to uniform GND distribution and promoted uniform stress distribution. We show that the trade-off between strength and ductility in carbide-modified IN718 can be overcome by careful PBF-LB/M processing and heat treatment.

Dual Control of Macrolithotype and Coal Structure on the Pore Parameters of Middle Jurassic Coals in the Southern Junggar Basin, NW China

Dual Control of Macrolithotype and Coal Structure on the Pore Parameters of Middle Jurassic Coals in the Southern Junggar Basin, NW China

Evaluation of gold mineralisation potential using AHP systems and weighted overlay analysis

The demand for sustainable development goals and the absence of systematic development and organised exploration for gold has prompted this study to integrate magnetic and radiometric datasets with lithology to evaluate the gold mineralisation potential in the Ilesha schist belt. This study considers 3168.72 km2 of the Ilesha schist belt in southwestern Nigeria, a frontier belt for gold deposits. The high-resolution airborne magnetic and radiometric datasets were processed using enhancement techniques, including the analytical signal, lineament density, and K/Th ratio. CET grid analysis, Euler deconvolution, and analytical signal depth estimation methods were used to aid the interpretation. The spatial integration and interpolation were performed using the Analytical Hierarchy Process (AHP) and weighted overlay analytical tools within the ArcGIS environment. The dominant structural controls for potential mineralisation are ENE–WSW and ESE–WNW trends. The depth of the magnetic sources revealed by the analytical signal ranged from 63.17 to 629.47 m, while depths ranging from 47.32 to 457.22 m were obtained from Euler deconvolution. The delineated highly magnetic edge sources, dense lineaments, radiometrically highlighted alteration zones, and lithological hosts for gold mineralisation were integrated to establish the gold mineralisation potential map. The AHP deductions reveal that 10.52% of the study site is within the high mineralisation potential class, a remarkable 60.39% falls within the moderate class, a significant portion (28.86%) falls within the poor class, and 0.23% is considered unfavourable. The result was optimised by validation using known mines, with 94% (i.e., 15 out of 16 mining sites) plotting within the high mineralisation potential class. This assessment provides invaluable insight for stakeholders and policymakers to embark on gold exploration and exploitation and promote sustainable mineral development.

Distributed Embedded System for Multiparametric Assessment of Infrastructure Durability Using Electrochemical Techniques.

We present an autonomous system that remotely monitors the state of reinforced concrete structures. This system performs real-time follow-up of the corrosion rate of rebars (iCORR), along with other relevant parameters such as temperature, corrosion potential (ECORR), and electrical resistance of concrete (RE), at many of a structure's control points by using embedded sensors. iCORR is obtained by applying a novel low-stress electrochemical polarization technique to corrosion sensors. The custom electronic system manages the sensor network, consisting of a measurement board per control point connected to a central single-board computer in charge of processing measurement data and uploading results to a server via 4G connection. In this work, we report the results obtained after implementing the sensor system into a reinforced concrete wall, where two well-differentiated representative areas were monitored. The obtained corrosion parameters showed consistent values. Similar conclusions are obtained with ECORR recorded in rebars. With the iCORR follow-up, the corrosion penetration damage diagram is built. This diagram is particularly useful for identifying critical events during the corrosion propagation period and to be able to estimate structures' service life. Hence, the system is presented as a useful tool for the structural maintenance and service life predictions of new structures.

Controlling lamination and directional growth of β-sheets via hydrophobic interactions: The strategies and insights

The self-assembling morphologies of proteins, nucleic acids, and peptides are well correlated with their functioning in biological systems. In spite of extensive studies for the morphologies regulating, the directional control of the assembly morphology structure for the peptides still remains challenging. Here, the directional structure control of a bola-like peptide Ac-KIIF-CONH2 (KIIF) was realized by introducing different amount of acetonitrile to the system. The morphologies were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the secondary structure was evaluated by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that the introducing of different amount of acetonitrile has significantly tuned the hydrophobic interactions amongst the side chains, thus affecting the self-assembling morphologies. As acetonitrile content increased, the assemblies changed from nanotubes to helical/twisted ribbons and then to thin fibrils, with a steady decrease in the width. In contrast, the assemblies changed from thin fibrils to helical/twisted ribbons, and then to matured nanotubes, exhibiting a steady increase in the width with peptide concentration increasing. Complementary molecular dynamics (MD) simulations demonstrated the important role of acetonitrile in controlling the hydrophobic interactions, providing microscopic evidence for the structure transition process. We believe such observations provide important insights into the design and fabrication of functional materials with controlled shape and size.

Quasi-One-Dimensional Zigzag Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution from Water.

Covalent organic frameworks (COFs) have potential applications in a wide range of fields. However, it remains a critical challenge to constrain their covalent expansions in the one-dimensional (1D) direction. Here, we developed a general approach to fabricate 15 different highly crystalline COFs with zigzag-packed 1D porous organic chains through the condensation of V-shaped ditopic linkers and X-shaped tetratopic knots. Appropriate geometrical combinations of a wide scope of linkers and knots with distinct aromatic cores, linkages, and functionalities offer a series of quasi-1D COFs with dominant pore sizes of 7-13 Å and surface areas of 116-784 m2 g-1. Among them, nitrogen (N)-doped 1D COFs with site-specific doping of heteroatoms favor a tunable control of band structures and conjugations and thus allow a remarkable hydrogen evolution rate up to 80 mmol g-1 h-1 in photocatalytic water splitting. This general strategy toward programming function in porous crystalline materials has the potential to tune the topologically well-defined electronic properties through precisely periodic doping.

How substrate surface area and surface curvature determine kinetics and titanate formation during non-hydrothermal alkali treatment of titanium microspheres

Titanium surface nanostructuring using alkali treatment gains significant attention in a wide range of fields, such as biomaterials, (photo)catalysis, (metal/ion) sorption, CO2 capture, electrochromism and sodium-ion batteries. Even though the physicochemical properties and application potentials of the surface nanostructures are fairly well understood, there is still debate about their exact formation mechanism, limiting knowledge based structural control through altered synthesis conditions. Moreover, this knowledge is largely focused on hydrothermal synthesis conditions, whereas non-hydrothermal conditions might provide benefits towards industrial application. Also the impact of substrate properties, rather than chemical reaction conditions, on the nanostructure formation is only limitedly reported in literature. This work reveals new fundamental knowledge of non-hydrothermal alkali treatment of titanium, using microspheres by implementing, for the first time, in-situ hydrogen measurement during alkali treatment in combination with the ex-situ determination of the sodium and oxygen content in the recovered alkali treated samples, providing critical information on the role of dissolution apart from the precipitation process. The effect of surface area and surface curvature on the dissolution and precipitation process, and the resulting impact on the physicochemical properties of the obtained titanate layer is studied. This shows the much larger impact on dissolution in contrast to precipitation, knowledge that is lacking in literature, but important when implementing alkali surface nanostructuring on complex (e.g. 3D printed) substrates, and considering the prospective shift from lab-scale to industry. The Ti dissolution step was found to be mainly controlled by the total surface area, while the rate determining step was found to be the titanate precipitation, not influenced by either surface area or particle size.The changes in oxygen content in the samples after transformation of titanate into TiO2 provided a novel method for its quantification. The microspheres were analysed chemically (Raman), structurally (XRD) and morphologically (SEM, MIP), screening the effect of surface area, particle size and reaction time on the growth behaviour of the titanate layer. The porous layer structurally corresponds to Na2Ti2O4(OH)2 for all evaluated conditions, with pores in the range of 10–600 nm. Increasing surface area and particle size results in local and non-uniform titanate growth, while titanate nanowire and strut formation between the microspheres were enhanced by reduced microsphere size and prolonged reaction times.

Metallogenic model of the Lykling ophiolite-hosted lode Au deposit, Scandinavian Caledonides: Insight from fluid inclusions, mineral chemistry and stable isotope geochemistry

The Lykling lode Au deposit represents a unique example of gold mineralization in the Upper Allochthone of the Scandinavian Caledonides. The mineralization is hosted by the Early Ordovician Lykling Ophiolite Complex and the intruding trondhjemite unit and spatially associated with two generations of mafic dykes that crosscut both the ophiolitic complex and trondhjemite. Field observations indicate that the mafic dykes did not play an active role in the emplacement of Au at Lykling, however their contacts with the immediate host rocks (i.e., gabbro and trondhjemite) may have focused ore-forming fluids.Three main stages in the evolution of the hydrothermal system in the Lykling area are documented by two generations of auriferous quartz veins: 1) older quartz-carbonate veins hosted by moderately angled brittle-ductile shear zones and 2) younger quartz-sulfide veins that fill steeply dipping brittle faults. Stage 1 resulted in deposition of barren quartz and gold-free pyrite from moderately saline NaCl-CaCl2-H2O ± CO2 fluids at temperatures between ∼310–330 °C and pressures in the range from 2.7 to 3.5 kbars. Under the given physicochemical conditions Au was mobile in the form of its chloride complexes. Stage 2 is associated with multiple episodes of ductile deformation punctuated by concomitant brecciation reflecting brittle-ductile transition processes. Fluid inclusion data reveals a decrease in temperature and pressure that may result in the formation of stable Au-bisulfide complexes and making the hydrothermal mobility of Au sensitive to changes in pressure. Consequently, the fluctuation in pressure controlled by the development of brittle-ductile structures likely resulted in the precipitation of native gold in quartz veins. Stage 3 represents a pure brittle event which is accompanied by a significant decrease in the fCO2/fS2 ratio. Mixing of higher-temperature and moderate-salinity fluids with cooler fluids has been recognized as the principal trigger for deposition of sulfides and a paragenetically late phase of native gold in the Lykling hydrothermal system.The Lykling ophiolite-hosted lode Au deposit shows numerous similarities with orogenic gold deposits elsewhere, including structural controls during mineralizing events, deposition from moderately to low salinity CO2-bearing aqueous solutions, deposition from a focused fluid flow along trans-crustal fault zones with a mixed brittle-ductile character and the spatial association with regionally metamorphosed terranes. In contrast to the great majority of the known orogenic gold deposits, the Lykling ophiolite-hosted lode Au deposit records a magmatic origin of volatiles. Therefore, taking into consideration field relationships and the regional setting of the Lykling deposit, we argue that its formation is concomitant with emplacement of the Sunnhordland Batholith during post-collisional thinning of the crust and associated localized uplift within the Lykling Ophiolite Complex.

Nonlinear optimal frequency control for dynamic vibration absorber and its application

A principal limitation of passive dynamic vibration absorber (DVA) lies in its intrinsic design constraint, as it is tuned to a specific resonant frequency, rendering it less effective at mitigating vibrations over a variable frequency range. To ensure that the DVA retains its vibration reduction capability under loads with time-varying frequencies, this paper proposes a method for designing the optimal suspension frequency based on the external load frequency. The approach involves altering the stiffness of the DVA through semi-active or active control to achieve the optimal suspension frequency and the best vibration reduction performance. In this study, the ratio R between the optimal suspension frequency and the load frequency is defined, and the nonlinear characteristic of R, based on the lowest vibration transmission rate, is studied using a two degree-of-freedom DVA model. Furthermore, an optimal suspension frequency variation control strategy based on load frequency identification is presented. Combined with the typical load with time-varying frequency encountered in metro vehicles, a multi-body dynamics theoretical model and a rigid–flexible coupling dynamics model are established to verify the effectiveness of the nonlinear optimal frequency control. Finally, the full-size railway vehicle roller rig is used to verify the correctness of the principle of optimal frequency curve. The research results show that when the mass ratio is 0.1, compared with rigid suspension, the nonlinear optimal frequency control can reduce the root mean square (RMS) value of the carbody’s entire time period acceleration during variable speed operation by 62.2%, and the maximum RMS value is reduced by 83.6%. In nonlinear control, unlike passive DVA, the vibration is never higher than that of rigid suspension within a specific velocity range. Compared with linear control strategy, nonlinearity can further reduce the elastic vibration. The test results from roller rig indicate that the semi-active DVA can effectively reduce the elastic vibrations of the carbody, while also validating the correctness of the nonlinear optimal suspension frequency principle. Therefore, the nonlinear frequency control in this study can provide reference for structural vibration control under loads with time-varying frequencies.

CaLi2PN3 - A Quaternary Chain-Type Nitridophosphate by Medium-Pressure Synthesis.

Nitridophosphates are in the focus of current research interest due to their structural versatility and properties, such as ion conductivity, ultra-incompressibility and luminescent properties when doped with suitable activator ions. Multinary representatives often require thorough investigation due to the competition with the thermodynamically more stable binary and ternary compounds. Another point of concern is the synthetic control of structural details, which is usually limited by conventional bottom-up syntheses. In this study, we report on the synthesis and characterization of the quaternary nitridophosphate CaLi2PN3. Various synthesis protocols were used for the preparation of CaLi2PN3, including the novel nitridophosphate double salt approach. The crystal structure was solved and refined from single-crystal X-ray diffraction data and confirmed by Rietveld refinement, solid-state NMR spectroscopy, EDX measurements and low-cost crystallographic calculations. The experimental results were corroborated by DFT calculations, which revealed the electronic band structure. Formation energy calculations allowed conclusions to be drawn about the stability in comparison to the initial ternary nitridophosphates. The synthesis of CaLi2PN3 exemplifies the enormous potential of medium-pressure syntheses in the field of nitridophosphate research. Furthermore, the presented new synthesis route allows a certain degree of structural control, which is a promising addition to previous synthesis strategies in nitridophosphate chemistry.