Space Group Immm Research Articles

Extending interstitial tetrelides into carbides: synthesis and crystal and electronic structures- of RE2Co2AlC (RE = La, Pr, Nd).

New quaternary compounds RE2Co2AlC (RE = La, Pr, Nd) of the filled W2CoB2 structure type were synthesized by the reaction of samples with the nominal composition RE40Co40Al20 (RE = La, Pr, Nd) and carbon. Single crystal X-ray diffraction data show that the RE2Co2AlC compounds crystallize in a body-centered orthorhombic space group Immm (oI12) with Z = 2 and a = 4.1841(11) Å, b = 6.1161(15) Å, c = 9.091(2) Å (La2Co2AlC); a = 4.1290(9) Å, b = 6.1152(18) Å, c = 8.844(3) Å (Pr2Co2AlC); a = 4.1168(15) Å, b = 6.1131(17) Å, c = 8.792(5) Å (Nd2Co2AlC) and are isotypic to the recently reported Nd2Co2SiC. The structures can be described as interstitial carbides of the W2CoB2 structure type with carbon atoms fully occupying the octahedral voids, which leads to the anisotropic expansion of the unit cell, more pronounced along the b-axis. Electronic structure calculations predict the RE2Co2AlC (RE = La, Pr, Nd) compounds to be metallic. The relative stability of the La2Co2AlX structures where X = C, O, Si, or a vacancy was investigated based on the bonding analysis, which emphasizes the important role that carbon plays in stabilizing the structural motif.

First-principles calculations to investigate physical properties of three magnetic sub lattice CaCu3Mn4-xIrxO12 (x = 0, 2 and 4) system via symmetry evaluation

Structural, electronic, elastic and magnetic properties of CaCu3Mn4-xIrxO12 (x = 0, 2 and 4) along with the optical properties of CaCu3Mn4O12 perovskites have been carried out in the framework of density functional theory (DFT). The investigation of structural optimization reveals that CaCu3Mn2Ir2O12 is stable in Pn-3 space group and CaCu3Mn4O12 and CaCu3Ir4O12 perovskites are stable in Im-3 space group. The cohesive energy and enthalpy of formation reveal the stability of these compound and shows that CaCu3Mn2Ir2O12 is more stable than the rest compounds. Substitution of Ir by Mn not only transforms these compounds from semiconductor to metallic nature but also transform the host compound from ferrimagnetic to anti-ferromagnetic via spin glass state. The DFT electronic behavior is also supported by the electrical resistivity. Elastic properties demonstrate the mechanical stability, anisotropic and ductile nature of these compounds. The optical properties indicate that CaCu3Mn4O12 is optically active for infrared electromagnetic radiations and could be used in optical devises. The ferrimagnetic ductile nature of CaCu3Mn4O12, spin glass and anti-ferromagnetic nature of CaCu3 Mn2Ir2O12 and CaCu3Ir4O12 makes these perovskites suitable candidates for spintronic and magnetic cloaking applications.

Tetrahedrite-(Ni), Cu6(Cu4Ni2)Sb4S13, the first nickel member of tetrahedrite group mineral from Luobusa chromite deposits, Tibet, China

Abstract Tetrahedrite-(Ni) (IMA2021-031), ideally Cu6(Cu4Ni2)Sb4S13, is the first natural Ni-member of tetrahedrite group mineral found in Luobusa chromite deposit, Tibet, China. The new species occurs as anhedral grains 2 to 20 μm in size, associated with gersdorffite, vaesite, and chalcostibite, which are disseminated in a matrix of dolomite, magnesite, quartz, Cr-rich mica, and Cr-bearing clinochlore. Tetrahedrite-(Ni) is black in color with a reddish-black streak and metallic luster. It is brittle with uneven fractures and has a calculated density of 5.073 g·cm–3. The mean values of 9 electron microprobe analyses (wt%) are Cu 39.83, Ni 5.67, Fe 1.45, Sb 21.69, As 5.45, S 25.39, total 99.48, and the empirical formula calculated on the basis of cation = 16 apfu is M(2)Cu6.00M(1)[Cu4.03(Ni1.55Fe0.42)Σ1.97]Σ6.00X(3)(Sb2.85As1.16)Σ4.01S12.67. Tetrahedrite-(Ni) is cubic, with space group I43m, a = 10.3478(4) Å, V = 1108.00(14) Å3, and Z = 2. Its crystal structure has been solved by X-ray single-crystal diffraction on the basis of 188 independent reflections, with a final R1 = 0.0327. Tetrahedrite-(Ni) is isostructural with tetrahedrite group minerals. It represents the first natural tetrahedrite-group mineral with a Ni-dominated charge-compensating constituent. Tetrahedrite-(Ni) may be the product of late-serpentinization at moderately high-temperature conditions around 350 °C. In this case, tetrahedrite-(Ni) and its mineral paragenesis record an entire geological process of nickel enrichment, migration, activation, precipitation, and alteration from deep mantle to shallow crust.

Effect of transition metals on the crystal field in CeCo0.4Fe0.6Ge3

We present an investigation of the influence of the 3d elements, Co and Fe, on the interactions between magnetic Ce atoms in the CeCo0.4Fe0.6Ge3 alloy, the member of the CeCo1−xFexGe3 series. The investigated alloy crystallizes in the noncentrosymmetric tetragonal BaNiSn3-type structure (space group I4mm, No. 107), in which the Co and Fe atoms occupy the same 2a position. The close vicinity to the quantum critical point for this alloy was indicated based on previous reports and confirmed by our low temperature resistivity measurements presented in this article. The role of Co and Fe atoms in this alloy was deduced from the scheme of the crystal field levels employing inelastic neutron scattering, specific heat, and magnetic susceptibility. For the analysis, samples LaCoGe3, LaFeGe3, and LaCo0.4Fe0.6Ge3 were used as non-magnetic analogs. The obtained results for CeCo0.4Fe0.6Ge3 alloy were compared with those for CeCoGe3 and CeFeGe3 compounds to emphasize the observed changes in physical properties. The specific heat results are supported by the first-principles calculations. The analysis indicated that the excitation levels of Ce ions are different for the Co- and Fe-rich neighborhood. Based on this information, we can conclude that the 3d elements provide the same energies of RKKY and Kondo interactions for the nearest Ce ions, but their energies for the further ions are lowered due to the presence of other 3d elements.

Stable nitrogen-rich yttrium nitrides under high pressure

Polynitrides have excellent physical and chemical properties as well as have drawn wide attention. Through the first-principles calculations and CALYPSO structure searching approach, we calculated the overall structure of YN components (from 0.5 to 10) and established the pressure versus composition diagram and pressure versus structure phase diagram of the YN system. This paper focuses on the YN2 structure (space group P21) which can be stable at 0 GPa and the YN10 structure with the highest nitrogen content (space group Imm2) with the intriguing chain-like N10 cage structure appears. Under ambient conditions, the YN10 structure has a high energy density (9.33 kJ g−1). By calculating the phonon dispersion curve, the structure has better dynamic stability at 250 GPa. Seven structures (Y2N, YN, YN2, YN3, YN5, YN8, YN10) that appear on convex hull graphs in all YN systems are also calculated. Their dynamics, mechanics and related electronic properties are described in the appendix. We hope that our theoretical research can facilitate future experimental realization and help to advance the research on nitrogen chains.

Colossal dielectric properties of Li- and Sm- based perovskite ceramics: A combination of first-principles calculations and experiments

The Li1/2Sm1/2Cu3Ti4O12 ceramic, which is in the ACu3Ti4O12 class, was investigated by means of both experimental and theoretical approaches. In our experiments, it was made via a solid-state reaction. Our XRD measurements revealed that the crystal structure of this sintered ceramic possesses a body-centered cubic system with an Im3 space group. Moreover, CuO and Sm4Ti3O12 impurity phases were observed. At 1 kHz and 20 °C, a high dielectric constant of approximately 3615–3838 and a rather low loss tangent of 0.119–0.185 were achieved for Li1/2Sm1/2Cu3Ti4O12 ceramics. According to our density functional theory calculations, we found that Li and Sm ions preferably occupy Cu and Ca sites, respectively. From our electron density analysis, there is a charge transfer from Li to Sm in this ceramic, although the valence states of Cu and Ti are constant. Cu+ and Ti3+ ions were detected by incorporating an oxygen vacancy into this structure. Based on our results, an internal barrier layer capacitor is a significant contributor to the enormous dielectric characteristics of this ceramic.

Critical behavior at paramagnetic to ferrimagnetic phase transition in A-site ordered perovskite CaCu3Cr2Nb2O12

A new perovskite-type oxide, CaCu3Cr2Nb2O12, has been synthesized at 10 GPa and 1100 °C. The compound crystallizes in space group Im3¯ with 1:3 ordered Ca and Cu cations at the A sites and disordered Cr and Nb cations at the octahedral B sites. CaCu3Cr2Nb2O12 exhibits a paramagnetic–ferrimagnetic transition at around 192.3 K and the Arrott plots manifest this transition is a second-order transition. We investigate the critical behavior of CaCu3Cr2Nb2O12 using the modified Arrott plots, Kouvel–Fisher plot, and the scale theory. The estimated critical exponents β, γ and δ, which yield β = 0.465 ± 0.006, γ = 1.312 ± 0.019 and δ = 3.833 ± 0.019 with TC = 197 K, fall within the predicted values from the mean-field model and three-dimensional Heisenberg model. The renormalization group analysis suggests that the exchange interaction decays as J(r)∼ r−4.871, indicating the magnetic interactions may be long-range coupling in CaCu3Cr2Nb2O12.

Phase relations, structure, properties and DFT study of compounds in the Sc-rich part of the systems Sc-{Mn,Fe,Co,Ni}-Ga

Phase relations, structure, properties and DFT study of compounds in the Sc-rich part of the systems Sc-{Mn,Fe,Co,Ni}-Ga

Thorium dicarbide under high pressure and high temperature: Ab initio investigation

A systematic study on the structural stability of thorium dicarbide (ThC2) under hydrostatic compression has been carried out by exploiting the evolutionary structure search algorithm as implemented in the universal structure predictor: evolutionary Xtallography (USPEX) code in conjunction with the ab initio electronic band structure calculation method. At ambient conditions, ThC2 exists in a monoclinic crystallographic phase with space group (SG) C2/c. Our calculations under generalized gradient approximation (GGA) predict the high-pressure structural sequence of monoclinic-I (SG C2/c) → monoclinic-II (SG C2/m) → orthorhombic-I (SG Pmma) → orthorhombic-II (SG Immm) → hexagonal (SG P6/mmm) for this material with transition pressures of ∼3.3, 58.3, 191.6, and 255 GPa, respectively. Out of this theoretically predicted high-pressure structural phase transition sequence, only the first transition, i.e., monoclinic-I → monoclinic-II, could be compared with the available high-pressure experimental study by Guo et al. [Sci. Rep. 7, 45872 (2017)]. The theoretically determined phase transition qualitatively agrees with the experimental results [Y. Guo et al. Sci. Rep. 7, 45872 (2017)]. Interestingly, our predicted intermediate orthorhombic-I (SG Pmma) phase has an enthalpy lower than that of the previously predicted orthorhombic Cmmm phase by Guo et al. [Sci. Rep. 7, 45872 (2017)]. The high-pressure structural sequence so predicted through static lattice calculations has been further substantiated by confirming the elastic and lattice dynamic stability of each structure in the pressure regime of its structural stability. Additionally, the superconducting transition temperature for all these structures has been determined and it is found that the monoclinic-II (C2/m) phase has the highest transition temperature of 17 K at 5 GPa. Furthermore, the thermo-physical properties along with the temperature-induced phase transitions in ThC2 have also been investigated through both the lattice dynamic simulations (within quasi-harmonic approximation) and ab initio molecular dynamics simulations.

Multiple magnetic transitions and magnetocaloric effect of Tb4CoIn alloy

We report on the magnetic, magnetocaloric, thermal, and electrical transport properties of Tb4CoIn alloy, which crystallizes in two phases, Tb6Co2.1In0.8 (space group Immm) and Tb2In0.9Co0.1 (space group P63/mmc), respectively. The alloy reveals three successive magnetic transitions around T1 (163 K), T2 (50 K), and T3 (29 K), respectively, associated with paramagnetic to ferromagnetic transition and two sequential antiferromagnetic transitions. The low-temperature transition T3 follows the first-order magnetic behavior and exhibits the field-induced magnetic transition. Meanwhile, T2 and T1 are found to be second-order in nature which opens a possibility for hysteresis-free magnetocaloric application. The magnetocaloric properties are determined using different magnetocaloric figures of merits such as –ΔSM, ΔTad, RCP, and TEC (10). Additionally, the universal curve behavior in the isothermal entropy change unveils the variation in critical exponents around T1 and T2 due to the magnetic inhomogeneity in the alloy. Besides, the electrical transport properties of the metallic alloy denote the maximum magnetoresistance of −10% around T1.

Study of dielectric properties of CaCu3Ti4O12 synthesized via different routes: Effect of sintering temperature

In this paper, the dielectric performance of calcium copper titanate (CCTO) synthesized by various possible routes is investigated. The effect of sintering temperature on dielectric, structural, morphological properties is conferred in text. X-ray diffraction spectroscopy reveals the presence of Im3 space group and body centred cubic structure. The results confirmed that 950 °C temperature is appropriate temperature for synthesis of oxide via various routes. The average particle size of CCTO is estimated to be 500 nm by field emission scanning electron microscope. The good capacitive dielectric performance of 500 °C and 1000 °C temperature sintered pellets is examined by LCR meter at frequency range of 40 Hz to 8 MHz. It is quite evidenced that oxalate co-precipitation and sono-chemical technique attributed to remarkable dielectric permittivity of 12,000 and 10,980 with minimum dielectric loss at high sintering temperature, as the temperature plays a major role in drastic enhancement in dielectric performance of a perovskites.

Colossal dielectric properties of Na1/3Ca1/3Sm1/3Cu3Ti4O12 ceramics: Computational and experimental investigations

A modified sol−gel technique was used to synthesize a high dielectric ceramic, Na1/3Ca1/3Sm1/3Cu3Ti4O12. The crystal structure of this sintered ceramic matches the standard pattern of a body−centered cubic (bcc) system within the Im3 space group (JCPDS No. 75–2188). No impurity phases were observed. Interestingly, a high dielectric permittivity of ∼1.14–1.35 × 104 and a low loss tangent of ∼0.027–0.039 were achieved in this sintered Na1/3Ca1/3Sm1/3Cu3Ti4O12 ceramic. Our DFT calculations disclosed that substitution of Na+ ions at Cu2+ sites causes an observed excess Cu concentration. As a result, metastable insulating phases were formed at a relatively high sintering temperature. Additionally, our electron density calculations revealed that Na ions lose their electrons to Sm ions, whereas the oxidation states of Cu and Ti are unaltered. Our results show that Cu+ and Ti3+ were observed after introducing an oxygen vacancy into this lattice. Significantly different values of Rg, Rgb, and Eg, Egb support an internal barrier layer capacitor as the most likely origin of the giant dielectric properties of this ceramic. XPS results show mixed Cu+/Cu2+ and Ti3+/Ti4+ in all ceramics, suggesting that electron hopping between Cu+↔Cu2+ and Ti3+↔Ti4+ is the probable origin of the n−type semiconducting state inside the grains.

Structural Characterization and Dynamics of a Layered 2D Perovskite [NH3(CH2)5NH3]MnCl4 Crystal near Phase Transition Temperature

[NH3(CH2)5NH3]MnCl4 crystals are grown via slow evaporation, and the crystal undergoes a phase transition at 298 K (TC) according to differential scanning calorimetry, and the structures determined via X-ray diffraction at 173 and 333 K are orthorhombic systems in the space group Imma. These results differed slightly from those previously reported, and the reasons for this are analyzed. The thermal stability is relatively high, with a thermal decomposition temperature of approximately 570 K. The 1H spin-lattice relaxation times t1ρ exhibited very large variations, as indicated by the large thermal displacement around the 1H atoms, suggesting energy transfer at ~TC, even if no structural changes occurred. The influences of the chemical shifts of 1H of NH3 and short t1ρ of C1 adjacent to NH3 in cation are insignificant, indicating a minor change in the N−H⋯Cl hydrogen bond related to the coordination geometry of the MnCl6 octahedron. These properties will be make it a potential application for eco-friendly solar cells.

Structural and magnetic properties of LaBa1-Sr CuFeO5+δ and YbBa1-Sr CuFeO5+δ (x = 0, 0.25 and 0.5) ceramic systems

We present a systematic study of structural and magnetic properties of LaBa1-xSrxCuFeO5+δ (La-x) and YbBa1-xSrxCuFeO5+δ (Yb-x) (x = 0.0, 0.25 and 0.5) ceramic compounds, synthesized with solid-state method. X-ray powder diffraction (XRD) technique indicates that La-x and Yb-x systems present single phases consistent with an orthorhombic symmetry (space group Immm (71)) and tetragonal symmetries (space group P4mm (99)), respectively, and a decreasing lattice parameter as the content of Sr increases. The results of infrared spectrums show the typical energy bands of a perovskite with a layered structure, and surface morphologic analysis evidenced the formation of polycrystalline material with diverse grain shape. The compositional characterization, obtained via the energy-dispersive X-ray spectroscopy technique, suggests that we achieve the desired material stoichiometry with the absence of impurities. Finally, vibrating sample magnetometry measurements evidenced an antiferromagnetic transition at a temperature around the 160 K only for x = 0, which is attributed to the dominant magnetic moments of rare earth ions.

Flux crystal growth of rubidium–iron silicates and germanates and their ion-exchange using alkali nitrate salts

Single crystals of two new rubidium ferrites, RbFeSiO4 and RbFeGeO4, were grown out of a eutectic RbCl–RbF melt. Both compounds crystallize in the noncentrosymmetric orthorhombic space group Ima2 and exhibit a three-dimensional porous framework structure composed of statistically disordered (Fe/T)O4 (T = Si, Ge) tetrahedra that corner-share to generate large channels running down the c-axis. These channels are occupied by Rb ions to maintain charge balance. RbFeSiO4 can also be prepared via a solid-state reaction by mixing and heating stoichiometric amounts of Rb2CO3, Fe2O3 and elemental Si; however, a similar approach for preparing RbFeGeO4 yielded a mixture of RbFeGeO4 and RbFeGe2O6. Powder second harmonic generation (SHG) measurements of RbFeSiO4 determined that the material is SHG-active with an intensity of 0.5 times of α-SiO2. First principles calculations in the form of density-functional theory indicated that it would be possible to ion exchange the Rb cation for other alkali metal cations. Applying a molten alkali nitrate salt-bath treatment at low soak temperatures of 350 °C–450 °C and short soak times of ∼16 h resulted in the almost complete replacement of rubidium with potassium and the partial replacement of rubidium with cesium, yielding K0.92Rb0.08FeSiO4, K0.91Rb0.09FeGeO4, and Cs0.48Rb0.52FeGeO4. No ion-exchange was observed when RbFeSiO4 was soaked in molten CsNO3; however, it was possible to force the exchange by using a CsCl melt at 680 °C to yield Cs0.13Rb0.87FeSiO4.

Successive magnetic transitions and broad refrigeration temperature span of Gd3Ni6Ga2

Magnetic ordering and magnetocaloric effect of polycrystalline Ce3Ni6Si2-type Gd3Ni6Ga2 (space group Im-3m, N 229, cI44) has been investigated via heat capacity and magnetic measurements. Gd3Ni6Ga2 exhibits ferromagnetic ordering at TC ​= ​104 ​K and a field-sensitive transformation of magnetic ordering at Tm ​= ​38 ​K. At 2 ​K, it is soft ferromagnetic with magnetic moment per Gd of 6.73 μB in 90 ​kOe. Heat capacity measurements in zero magnetic field indicated the Debye temperature around 320 ​K and peak in heat capacity around TC, only. Gd3Ni6Ga2 shows table-like magnetic entropy change of −4.9 ​J/kg⋅K at TC and −3.8 ​J/kg⋅K at Tm in a field change of 50 ​kOe with a wide working temperature range.

Hyaluronic-Acid-Tagged Cubosomes Deliver Cytotoxics Specifically to CD44-Positive Cancer Cells.

Delivery of chemotherapy drugs specifically to cancer cells raises local drug doses in tumors and therefore kills more cancer cells while reducing side effects in other tissues, thereby improving oncological and quality of life outcomes. Cubosomes, liquid crystalline lipid nanoparticles, are potential vehicles for delivery of chemotherapy drugs, presenting the advantages of biocompatibility, stable encapsulation, and high drug loading of hydrophobic or hydrophilic drugs. However, active targeting of drug-loaded cubosomes to cancer cells, as opposed to passive accumulation, remains relatively underexplored. We formulated and characterized cubosomes loaded with potential cancer drug copper acetylacetonate and functionalized their surfaces using click chemistry coupling with hyaluronic acid (HA), the ligand for the cell surface receptor CD44. CD44 is overexpressed in many cancer types including breast and colorectal. HA-tagged, copper-acetylacetonate-loaded cubosomes have an average hydrodynamic diameter of 152 nm, with an internal nanostructure based on the space group Im3m. These cubosomes were efficiently taken up by two CD44-expressing cancer cell lines (MDA-MB-231 and HT29, representing breast and colon cancer) but not by two CD44-negative cell lines (MCF-7 breast cancer and HEK-293 kidney cells). HA-tagged cubosomes caused significantly more cell death than untargeted cubosomes in the CD44-positive cells, demonstrating the value of the targeting. CD44-negative cells were equally relatively resistant to both, demonstrating the specificity of the targeting. Cell death was characterized as apoptotic. Specific targeting and cell death were evident in both 2D culture and 3D spheroids. We conclude that HA-tagged, copper-acetylacetonate-loaded cubosomes show great potential as an effective therapeutic for selective targeting of CD44-expressing tumors.

A study of structural, morphological, optical and humidity sensing properties of CaCu3Ti4O12 powders synthesized by combustion method

Calcium Copper Titanate (CCTO) powder was synthesized via a low-cost facile combustion method at various calcination temperatures and times. The structural properties of the prepared CCTO powder were investigated from an X-ray diffraction (XRD) study, which confirmed the formation of the cubic phase with space group Im3. Further, Rietveld refinement of the XRD data was performed for the detailed structural analysis of the samples. The surface morphology of the CCTO powder was studied by Field Emission Scanning Electron Microscopy (FESEM), which showed an increase in particle size with an increase in the calcination temperature. The optical properties of the powders were examined by UV–vis Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence Spectroscopy. The optical bandgap values, estimated from Tauc’s plot, increase with the increase in calcination temperature due to the elimination of structural defects or localized states inside the bandgap. The porous single-phase CCTO ceramic was subjected to a homemade experimental set-up combined with an LCR meter to investigate its room temperature humidity sensing characteristics in capacitive mode at various operating frequencies. At 100 Hz, the obtained humidity response curve for the CCTO-based sensor showed a 560 % increment in capacitance as the Relative Humidity (RH) changed from 40 % to 90 %.

Cycloidal Magnetic Ordering in Noncentrosymmetric EuIrGe3

Successive magnetic phase transitions at TN = 12.2 K, \(T'_{\text{N}} = 7.0\) K, and \(T_{\text{N}}^{*} = 5.0\) K in EuIrGe3, an intermetallic compound with a body centered tetragonal lattice belonging to a polar space group I4mm, has been investigated by neutron diffraction and resonant X-ray diffraction. It is shown that EuIrGe3 exhibits an incommensurate longitudinal sinusoidal order with \(\boldsymbol{q} \sim (0,0,0.792)\) and mq || c-axis in the high temperature phase (\(T'_{\text{N}} < T < T_{\text{N}}\)), which changes to a cycloidal order with \(\boldsymbol{q} = (\delta ',0,0.8)\) (δ′ ∼ 0.017) and mq || ac-plane in the intermediate phase (\(T_{\text{N}}^{*} < T < T'_{\text{N}}\)). In the low temperature phase (\(T < T_{\text{N}}^{*}\)), the cycloidal plane rotates by 45° to have \(\boldsymbol{q} = (\delta ,\delta ,0.8)\) (δ ∼ 0.012). It is also pointed out that the X-ray scattering amplitude from odd-parity magnetic quadrupole due to the polar environment interfere with that from normal even-parity magnetic dipole in the magnetic ordered phase.

Machine learning accelerated random structure searching: Application to yttrium superhydrides.

The search for new superhydrides, promising materials for both hydrogen storage and high temperature superconductivity, made great progress, thanks to atomistic simulations and Crystal Structure Prediction (CSP) algorithms. When they are combined with Density Functional Theory (DFT), these methods are highly reliable and often match a great part of the experimental results. However, systems of increasing complexity (number of atoms and chemical species) become rapidly challenging as the number of minima to explore grows exponentially with the number of degrees of freedom in the simulation cell. An efficient sampling strategy preserving a sustainable computational cost then remains to be found. We propose such a strategy based on an active-learning process where machine learning potentials and DFT simulations are jointly used, opening the way to the discovery of complex structures. As a proof of concept, this method is applied to the exploration of tin crystal structures under various pressures. We showed that the α phase, not included in the learning process, is correctly retrieved, despite its singular nature of bonding. Moreover, all the expected phases are correctly predicted under pressure (20 and 100GPa), suggesting the high transferability of our approach. The method has then been applied to the search of yttrium superhydrides (YHx) crystal structures under pressure. The YH6 structure of space group Im-3m is successfully retrieved. However, the exploration of more complex systems leads to the appearance of a large number of structures. The selection of the relevant ones to be included in the active learning process is performed through the analysis of atomic environments and the clustering algorithm. Finally, a metric involving a distance based on x-ray spectra is introduced, which guides the structural search toward experimentally relevant structures. The global process (active-learning and new selection methods) is finally considered to explore more complex and unknown YHx phases, unreachable by former CSP algorithms. New complex phases are found, demonstrating the ability of our approach to push back the exponential wall of complexity related to CSP.