Crystal Structure AnaLYsis By Particle Swarm Optimization Research Articles

Structural evolution and hydrogen storage properties of ScHn− (n = 10–20) clusters

An unbiased Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method combined with density functional theory (DFT) study was adopted to identify the ground state ScHn− (n = 10–20) isomers. We have performed a series of investigation of electronic properties, structural evolution, hydrogen storage properties of ScHn− (n = 10–20) clusters. Using time-dependent (TD-) DFT, the photoelectron spectra (PES) of the low-lying structures of ScHn− clusters have been simulated. The adsorption energies of ScHn− (n = 10–20) clusters are found in 2.52 eV-2.65 eV, and all hydrogen atoms are adsorbed on the Sc atom. Studied on the molecular orbitals and chemical bonds of the ScH12− cluster, it is found that the ScH12− cluster are mainly the interaction between the 3d atom orbital of Sc and the 1s atom orbital of H. The present study aims at novel nanomaterials for hydrogen storage.

Role of Edge Reconstruction in the Synthesis of Few-Layer Black Phosphorene.

Recent advancements in preparing few-layer black phosphorene (BP) are hindered by edge reconstruction challenges. Our previous studies have revealed the factors contributing to the difficulty of growing few-layer BP. In this study, we have successfully identified three reconstructed edges in bi- and multilayer BP through a combination of the crystal structure analysis by particle swarm optimization (CALYPSO) global structure search and density functional theory (DFT). Notably, the reconstruction between adjacent layers proves more beneficial than self-passivation or maintaining pristine edges. Among the reconstructed edges, the reconstructed ZZ edge is the most stable, regardless of the number of layers. Calculated electronic band structures reveal a significant transition in the electronic properties of black phosphorus nanoribbons (BPNRs), changing from metallic to semiconducting. This insight not only enhances the understanding of the fundamental properties of BP but also provides valuable theoretical guidance for the experimental growth of BPNRs or black phosphorus nanowires (BPNWs).

Exploring the structure and hydrogen storage capacity of CeHn0/+ clusters.

The unique 4f orbitals and abundant electronic energy levels of rare earth elements enable effective doping and modification to enhance hydrogen storage performance, making it an increasingly prominent focus of research. The structures of neutral and cationic CeHn0/+ (n = 2-20) clusters have been determined using the Crystal Structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method in conjunction with density functional theory (DFT). Interestingly, the CeH13 and CeH14+ exhibit remarkable stability in the doublet state with Cs and C2v symmetry, respectively. The adsorption energy of CeHn0/+ (n = 2-20) suggests a preference for H atoms to chemically adsorb on Ce atoms. The analysis of molecular orbital composition reveals that the stability of both CeH13 and CeH14+ is attributed to the significant hybridization between the H 1s and Ce 4f orbitals. Both CeH13 and CeH14+ demonstrate significant hydrogen storage capacities, with values reaching 8.5 wt% and 9.1 wt%, respectively.

Theoretical research on the geometric structure and electronic properties of medium-sized LaHnq (n=2–20, q=0, 1) clusters

In cluster scientific research, determining the ground state structure is a fundamental aspect of investigating the properties and applications of clusters. However, the determination of the lowest-energy structure of clusters is not only a complex global optimization problem but also a crucial challenge in current cluster research. In the work the geometric structure and electronic properties of LaHn0/+ (n = 2–20) nanoclusters with potential for hydrogen storage are investigated using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method and Density Functional Theory (DFT). By calculating the average adsorption energy and hydrogen storage mass fraction, it is predicted that neutral LaH13 and cationic LaH14+ clusters exhibit high hydrogen storage densities of 8.6 wt% and 9.2 wt%, respectively. Furthermore, the molecular orbital composition and internal chemical bond binding mode were analyzed using adaptive natural density partition (AdNDP) and natural bond orbital (NBO). The results indicate that the strong hybridization between La 5d orbitals and H 1s orbitals is the primary factor contributing to the high stability of both neutral LaH13 and cationic LaH14+ clusters.

Theoretical study on geometric structures and hydrogen storage in anionic CeH[formula omitted] ([formula omitted] = 2–20) nanoclusters

The geometric structures of anionic CeHn− (n = 2–20) clusters are obtained using crystal structure analysis by particle swarm Optimization(CALYPSO) and density functional theory(DFT). The SDD basis set for Ce atom and the all electron 6-311G ＋ ＋ (D, P) basis set for H atom are set respectively, and the lower-energy isomers in each size for CeHn− (n = 2–20) clusters are re-optimized at the B3LYP level. The photoelectron spectroscopy(PES) for the global minimum of anionic CeHn− (n = 2–20) clusters have been simulated using the Time-Dependent Density Function Theory(TD-DFT) method to determine the authenticity of all the lowest-energy structures obtained. The anionic CeH10− cluster with C2v point group symmetry and an excellent hydrogen storage capacity of 6.7 wt% has been discovered. Chemical bond analysis shows that the internal stability of anionic CeH10− cluster is primarily affected by the interaction between Ce 4f orbital and H 1s orbital, which is formed σ bond at the larger HLG of 4.78 eV. Furthermore, anionic CeH10− cluster has high hydrogen storage capacity, large adsorption energy and good stability, which is expected to be a new nanometer hydrogen storage material. The present work provides guidance for the future synthesis and design of new rare earth(RE) hydrogen storage nanomaterials.

A ten-fold coordinated high-pressure structure in hafnium dihydrogen with increasing superconducting transition temperature induced by enhancive pressure

High pressure is an effective method to induce structural and electronic changes, creating novel high-pressure structures with excellent physical and chemical properties. Herein, we investigate the structural phase transition of hafnium dihydrogen (HfH2) in a pressure range of 0 GPa–500 GPa through the first-principles calculations and the crystal structure analysis by particle swarm optimization (CALYPSO) code. The high-pressure phase transition sequence of HfH2 is I4/mmm → Cmma → P-3m1 and the two phase transition pressure points are 220.21 GPa and 359.18 GPa, respectively. A newly trigonal P-3m1 structure with 10-fold coordination first appears as an energy superior structure under high pressure. These three structures are all metallic with the internal ionic bonding of Hf and H atoms. Moreover, the superconducting transition temperature (T c) values of Cmma at 300 GPa and P-3m1 at 500 GPa are 3.439 K and 19.737 K, respectively. Interestingly, the superconducting transition temperature of the P-3m1 structure presents an upward trend with the pressure rising, which can be attributed to the increase of electron–phonon coupling caused by the enhanced Hf-d electronic density of states at Fermi level under high pressure.

Probing the effects of lithium doping on structures, properties, and stabilities of magnesium cluster anions

Bimetallic clusters have aroused tremendous interest because the property changes like structure, size, and composition have occurred. Herein, a structural search of the global minimum for anionic (n = 2–11) clusters is performed using an efficient crystal structure analysis by particle swarm optimization (CALYPSO) structural searching program with subsequent density functional theory (DFT) calculations. A great variety of low energetic isomers are converged, and the most stable ones are confirmed by comparing their total energy of each size. It is found that the clusters are structurally consistent with corresponding Mg clusters anions except for and . In all the doped clusters, the Li atom prefers to occupy the convex position. Simulated photoelectron spectra (PES), Infrared (IR), and Raman spectra of could be used as an essential evidence for identifying cluster structures experimentally in the future. Stability study reveals that a tower-like structure of has prominent stability and can be identified as a magic number cluster. The reason might be that there are both closed-shell 1S21P61D102S2 electronic configurations and stronger Li–Mg bonds caused by sp hybridization in the cluster.

Predicting novel atomic structure of the lowest-energy Fe n P13–n (n = 0–13) clusters: A new parameter for characterizing chemical stability

A series of novel atomic structure of lowest-energy Fe n P13–n (n = 0–13) clusters via density functional theory (DFT) calculations and an unbiased structure search using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code. Our research results show that the global minimum geometry structure of neutral Fe13–n P n (n = 0–6) clusters tend to form cage structures but the lowest-energy Fe13–n P n (n = 7–13) clusters are gradually evolution from a cage structure to a chain shape geometric structure. Their geometric structure should responsible for the raise of binding energy from Fe7P6 to P13 clusters rather than chemical components. This is completely different from a linear relation of the binding energy with chemical components in our previous research for Cu n Zr13–n (n = 3–10) clusters (J. Mol. Liq. 343 117603 (2021)). Hence, in order to characterize the global chemical stability of target cluster, we proposed a new parameter (jyq = η/χ) that the chemical hardness of isolated cluster is used to be divided by its electronegativity. One of the biggest advantages of this parameter is successful coupling the ability of a resistance to redistribution of electrons and the ability to attract electrons from other system (such as atom, molecular or metallic clusters). Moreover, it is found that the P13 cluster shows typical insulator characteristics but the Fe12P1 shows typical conductor characteristics, which phenomena can be attributed to the remarkable delocalized and localized electrons in Fe12P1 and P13, respectively. In terms of nearly-free-electron mode, we also found that the number of electrons on Femi level (N(E F)) are obviously tended to toward a lower value when Fe was replaced gradually with P from Fe13 to P13, and a non-magnetic can be observed in Fe13, Fe2P11, Fe1P12, and P13 that mainly because their perfect symmetrical between spin-up and spin-down of density of states of electrons.

Systematic investigation of structure and electronic properties of Cs doped anionic Bn clusters

Projects about boron-based doped of metals have constantly an important means of advancing its performance index, while bimetallic Cs atom doped of anion Bn− (n = 1–12) clusters have not been reported. In this work, the structure and electronic properties of the anionic Cs2Bn− (n = 1–12) clusters were investigated using the crystal structure analysis by particle swarm optimization (CALYPSO) structure search method and density functional theory (DFT). Theoretical calculations reveal that the most stable isomer comes from the Cs2B8− cluster with high symmetry, while the formation of two Cs atoms in different directions of pure Bn-2− is the primary structural evolution law. It is worth mentioning that the metallic character and magnetic properties of the Cs2Bn− (n = 1–12) clusters were all correspondingly enhanced after doping with Cs atoms. In addition, the dual-calibration scheme of the united photoelectron spectroscopy (PES) and infrared (IR) spectroscopy is helpful to easily verify the structural characteristics of Cs2Bn− (n = 1–12) clusters in different physical state situations. We further study the bonding characteristics of Cs2B8− clusters with high stability by using the adaptive natural density partitioning (AdNDP) and the electron localization function (ELF) methods. The results demonstrate that the 2px, 2py and part of 2s orbitals of the B-plane 2-center double-electron bond are the major contributors to the Cs2B8− cluster.

Pressure-directed mixed ionic–electronic to pure electronic conduction transition and enhanced grain boundary conductivity in solid electrolyte CdMoO4

Scheelite ABO4-type solid electrolytes have attracted much attention for potential applications as oxygen ionic conductors of solid oxide fuel cells. Herein, a systematic study was carried out on the electrical transport properties of CdMoO4 under high pressure by impedance spectroscopy measurements and theoretical calculations. The sequence of structural phase transitions at pressures was determined as I41/a → C2/c → P21/c by the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method. A pressure-induced conduction transition from mixed ionic–electronic to pure electronic conduction was observed. Below 25.6 GPa, O2− ions play a major role in the electrical transport process. The microscopic transport mechanism was analyzed with grain boundary energies and migration energy barriers. Above 26.9 GPa, the grain boundary response was weakened significantly after a pressure cycle, and the grain boundary conductivity increased by about three times due to pressure. These results provide guidelines for the optimization and application of scheelite ABO4-based oxygen ionic conductors in solid oxide fuel cells.

Prediction of a series of superhard BC4N structures

Six novel superhard BC4N-x (x = a, b, c, d, e, f) structures with low energies are determined by ab-initio evolutionary methodology using crystal structure analysis by particle swarm optimization (CALYPSO) code. These BC4N polymorphs employ a sp3-hybrid network with BN and C layers connected alternatively, and with low energies close to those of the previously proposed lowest energy c-BC4N. The possible precursors and phase transition paths from hBC4N-x to novel BC4N-x (x = a, b, c, d, e, f) are also determined, and the energies of the hBC4N-x are close to each other under ambient pressure. Moreover, simulated XRD patterns of these novel BC4N structures show agreement with experimental data. The Raman main peak positions and intensities of these structures are also consistent. All indications point out the experimentally synthesized samples likely contain various BC4N structures.

Theory-directed discovery of high-temperature superconductivity in clathrate hydrides at high pressure

Theory-directed discovery of high-temperature superconductivity in clathrate hydrides at high pressure

Study on structures, electronic, spectral and thermodynamic properties of lanthanide-doped boron-based MBn−(M=La, Ce, Pr; n=8, 9) clusters

Here we reported the structures, electronic, spectral and thermodynamic properties of MBn−(M = La, Ce, Pr; n = 8, 9) clusters using Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) searching method and density functional theory (DFT). Results found that the lowest structures of MBn−(M = La, Ce, Pr; n = 8, 9) possess the half-sandwich structure with Cs symmetry, respectively. Based on the lowest energy structures, the electronic properties are analyzed by calculating charge transfer, electron localization function and polarizability; the photoelectron spectra, infrared spectra, Raman spectra and UV-vis spectra are computationally simulated to facilitate their spectral characterizations. At last, thermodynamic properties are symmetrically investigated for doped systems. We believe that our research will provide useful motivation for further experimental and theoretical investigations of lanthanide-doped boron based nanomaterials.

First-principles calculations of local structure and electronic properties of Er<sup>3+</sup>-doped TiO<sub>2</sub>

Trivalent rare earth erbium ion (Er<sup>3+</sup>) doped titanium oxide (TiO<sub>2</sub>) can possess a very wide range of applications due to its excellent optoelectronic properties, thus standing out among many rare-earth-doped luminescent crystals. However, the issues regarding local structure and electronic properties have not been finalized. To address these problems, the CALYPSO (Crystal structure AnaLYsis by Particle Swarm Optimization) method combined with the first-principles calculations is employed, and many converged structures of Er<sup>3+</sup>-doped TiO<sub>2</sub> are successfully obtained. Further structural optimization is performed by using the VASP (Vienna <i>ab initio</i> simulation package) software package, and we report for the first time that the lowest energy structure of Er<sup>3+</sup>-doped TiO<sub>2</sub> has the <inline-formula><tex-math id="M2">\begin{document}$ P\overline 4 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221847_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221847_M2.png"/></alternatives></inline-formula><i>m</i>2 symmetry. It can be observed that the doped Er<sup>3+</sup> ions enter into the host crystal and occupy the positions of Ti<sup>4+</sup> ions, resulting in structural distortion, which eventually leads the local Er<sup>3+</sup> coordination site symmetry to reduce from <i>D</i><sub>2<i>d</i></sub> into <i>C</i><sub>2<i>v</i></sub>. We speculate that there are two reasons: 1) the difference in charge between Er<sup>3+</sup> ions and Ti<sup>4+</sup> ions leads to charge compensation; 2) the difference between their electron radii is obvious: the radius is 0.0881 for Er<sup>3+</sup> ion and 0.0881 for Ti<sup>4+</sup> ion. In addition, during the structural search, we also find many metastable structures that may exist at a special temperature or pressure, which play an important role in the studying of structural evolution. When the electronic band structure of the Er<sup>3+</sup>-doped TiO<sub>2</sub> system is calculated, we adopt the method of local density approximation (LDA) combined with the on-site Coulomb repulsion parameter <i>U</i> to accurately describe the strongly correlated system. For the specific value of <i>U</i>, we adopt 3.5 eV and 7.6 eV to describe the strong correlation of 3d electrons of Ti<sup>4+</sup> ions and 4f electrons of Er<sup>3+</sup> ions, respectively. According to the calculation of electronic properties, the band gap value of Er<sup>3+</sup> doped TiO<sub>2</sub> is about 2.27 eV, which is lower than that of the host crystal (<i>E</i><sub>g</sub> = 2.40 eV). The results show that the reduction in the band gap is mainly caused by the f state of Er<sup>3+</sup> ions. The doping of Er ion does reduce the band gap value, but it does not change the conductivity of the system, which have great application prospect in diode-pumped laser. These findings not only provide the data for further exploring the properties and applications of Er<sup>3+</sup>:TiO<sub>2</sub> crystals, but also present an approach to studying other rare-earth-doped crystalline materials.

Lowest-energy structural and electronic properties of CunZr13−n (n = 3–10) clusters in metallic glasses via CALYPSO search and density functional theory calculations

Bimetallic Cu–Zr clusters containing 13 atoms are intimately linked with the best glass former chemical compositions of Cu–Zr metallic glasses. Thus far, the ground-state geometric structures of CunZr13−n (n = 3–10) clusters have not been reported and are not well known because of the complexity of the energetic potential surface. In this study, a series of novel ground-state geometric structures of CunZr13−n (n = 3–10) clusters were found via an unbiased structure search using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code and density functional theory (DFT) calculations. Three new parameters for the second-order difference in energy gap, chemical hardness, and electronegativity were proposed to evaluate the relative chemical activity dependence of the chemical composition for the lowest-energy CunZr13−n (n = 3–10) clusters. Results show that although Cu5Zr8 and Cu7Zr6 are double-layered schistose and distorted face-centered cubic (FCC) structures, respectively, the lowest-energy structures of Cu–Zr clusters exhibit irregular nested structures based on a pentagonal bipyramid (existing nearly golden ratio order (NGRO)) with low symmetry, and the entire evolutionary configuration exhibits a stable transient from Cu3Zr10 to Cu10Zr3. Analysis of the electronic shell structure showed that the chemical compositions of Cu6Zr7 and Cu8Zr5 clusters have good correspondence with the best glass formers, Cu50Zr50 and Cu64Zr36, respectively, which is mainly due to the odd and even number of valence electrons rather than the geometric structure for a given Cu–Zr cluster. Moreover, the molecular orbital contours showed that the highest occupied molecular orbital and lowest unoccupied molecular orbital of the lowest-energy structure of CunZr13−n (n = 3–10) clusters are mainly contributed by the 4d electrons of Zr, which are consistent with the density of electronic states. The infrared spectra of the lowest-energy structure of CunZr13−n (n = 3–10) clusters provide a pathway for future experimental research.

Systematic investigation of geometric structures and electronic properties of lithium doped magnesium clusters

Geometric structures and electronic properties of Lithium doped magnesium clusters, LiMgn (n = 2–11), were investigated by utilizing Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) structural searching method with density functional theory (DFT) calculations. Theoretical calculations showed that the most stable isomers are three-dimensional structure from n ≥ 3, and appear a structural unit of the six-Mg triangular prism in their structures from n ≥ 8. Moreover, the Li atoms prefer to occupy the convex capped sites. Analyses of stabilities revealed that LiMg9 with high C4v symmetry possesses the highest stability and the doping of lithium atom makes the stabilities of magnesium clusters increase. Upon an analysis of charge transfer, charges transfer take place from Li to Mg atoms, and there exist strong sp hybridization between Li and Mg atoms with the increasing number of magnesium atoms. At last, further chemical bonding analysis indicated that there is a strong Li-Mg interaction in the LiMg9 cluster.

Investigation of the microstructure and electronic features for [formula omitted]-doped YAG crystal: A first-principle study

The Ce3+-doped YAG crystal has drawn considerable interest because of its important application in the white light-emitting diodes. However, the fundamental understanding of its microstructure is still lacking. In this work, the structural evolution and electronic properties of Ce3+-doped YAG crystal are systematically studied on the basis of the density functional theory (DFT) as well as Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) method. A novel stable phase with cage-like structure and C222 space group of Ce3+-doped YAG crystal has been reported. The calculations of the electronic band structure indicate that the Ce3+-doped YAG possesses a conductive character because the Fermi level is crossed through by the conduction band. By analyzing the electronic density of states (DOS), we conclude that the reason of the elimination of the insulated character can be attributed to the impurity Ce3+. The bond character between the Ce-O and Y-O are identified by the calculation of the electron localization function (ELF). These results can offer significant information for exploring new rare-earth doped laser materials and also provide useful insights to elucidate some experimental phenomena.

A density functional investigation on the structures, electronic, spectral and fluxional properties of VB20- cluster

By using a joint experimental and first principle calculation, in 2017, Li’s group reported a tubular molecular rotor, TaB20-, which possesses a Ta-centred eighteen-membered drum with a slight distortion and two bridging B atoms atop the drum. Moreover, the tubular B2-Ta@B18- presents a new type of internal rotation, the rotation with barrier of ΔE = 1.13 kcal/mol possesses nine equivalent positions with the rotation angle of 400 in each step [Chem. Commun. 53, 1587 (2017)]. Then, an interesting question arises: whether the other same group atoms dopant can form the similar frameworks? And if it is, whether the B2 unit can rotate relative to drum motif? In present work, with inspirations from research of tubular molecular rotor TaB20-, we present herein the possibility of the novel structures of VB20- cluster by using Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) searching method and first-principle theory calculations. The results indicated that VB20- cluster is composed of a V-centered eighteen-membered drum with a B2 unit on the top of drum. Based on the lowest energy structure of VB20- cluster, electronic properties are analyzed by calculating the molecular orbitals, charge transfer, Wiberg bond order and electron localization function. In addition, the infrared spectra, Raman spectra and photoelectron spectra are predicted and used to identify the structures from experiments. At last, based on detailed bonding analyses, the fluxional properties are analyzed systematically. We hope that knowledge obtained from this study can be helpful for future theoretical and experimental synthesis of novel vanadium-boride nanomaterials.

Exploration of the novel structures and electronic properties for Nd3+ doped CaTiO3

Rare-earth neodymium ions (Nd3+) doped CaTiO3 crystal shows excellent light-emitting properties which give rise to the development of new-generation laser devices. However, the structural evolutions of the trivalent Nd3+ doped CaTiO3 (CaTiO3:Nd) crystal are still not clear. Herein, we report a systematic first-principles study on the geometrical structures and electronic properties of CaTiO3:Nd. Based on the crystal structure analysis by particle swarm optimization (CALYPSO) method combined with density functional theory, we uncover a novel layered grid structure with Pm space group. The Ca2+ ion in the host crystal is replaced by the Nd3+ ion. The simulated XRD spectrums match fairly well with the experimental data, which demonstrating the validity of the obtained ground state structure. The calculated band structures manifest that the conduction band pass through the Fermi level, suggesting a conductive character of CaTiO3:Nd. The results of density of states (DOS) demonstrate that the impurity Nd3+ ions can trigger a phase transition of CaTiO3 from semiconductor to conductor. The analysis of electron localization function (ELF) for CaTiO3:Nd indicates that the interaction between Ca-O is mainly ionic bond. These results could provide significant insights for exploring new laser materials.

Reduction of dimerization tendency due to the decrease in hybridization index by inclusion of 4s and 4p semicore states as valence states in Mon (n = 2 − 18) clusters: A first-principles study

Owing to the unique structural, electronic, and physico-chemical properties, molybdenum clusters are expected to play an important role in future nanotechnologies. However, their ground states are still under debate. In this study, the crystal structure analysis by particle swarm optimization (CALYPSO) approach is used for the global minimum search, which is followed by first-principles calculations, to detect an obvious dimerization tendency in Mon (n = 2−18) clusters when the 4s and 4p semicore states are not regarded as the valence states. Further, the clusters with even number of atoms are usually magic clusters with high stability. However, after including the 4s and 4p electrons as valence electrons, the dimerization tendency exhibits a drastic reduction because the average hybridization indices Hsp, Hsd, and Hpd are reduced significantly. Overall, this work reports new ground states of Mon (n=11, 14, 15) clusters and proves that semicore states are essential for Mon clusters.