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1.
Int. braz. j. urol ; 50(6): 727-736, Nov.-Dec. 2024. tab, graf
Artículo en Inglés | LILACS-Express | LILACS | ID: biblio-1575093

RESUMEN

ABSTRACT Introduction: We aim to compare the safety and effectiveness of the KangDuo (KD)-Surgical Robot-01 (KD-SR-01) system and the da Vinci (DV) system for robot-assisted radical nephroureterectomy (RARNU). Materials and Methods: This multicenter prospective randomized controlled trial was conducted between March 2022 and September 2023. Group 1 included 29 patients undergoing KD-RARNU. Group 2 included 29 patients undergoing DV-RARNU. Patient demographic and clinical characteristics, perioperative data, and follow-up outcomes were collected prospectively and compared between the two groups. Results: There were no significant differences in patient baseline demographic and preoperative characteristics between the two groups. The success rates in both groups were 100% without conversion to open or laparoscopic surgery or positive surgical margins. No significant difference was observed in docking time [242 (120-951) s vs 253 (62-498) s, P = 0.780], console time [137 (55-290) min vs 105 (62-220) min, P = 0.114], operative time [207 (121-460) min vs 185 (96-305) min, P = 0.091], EBL [50 (10-600) mL vs 50 (10-700) mL, P = 0.507], National Aeronautics and Space Administration Task Load Index scores, and postoperative serum creatinine levels between the two groups. None of the patients showed evidence of distant metastasis, local recurrence, or equipment-related adverse events during the four-week follow-up. One (3.4%) patient in Group 2 experienced postoperative enterovaginal and enterovesical fistulas (Clavien-Dindo grade III). Conclusions: The KD-SR-01 system is safe and effective for RARNU compared to the DV Si or Xi system. Further randomized controlled studies with larger sample sizes and longer durations are required.

2.
World J Clin Cases ; 12(28): 6237-6240, 2024 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-39371553

RESUMEN

In this letter, we discuss the topic of necessity of routine laboratory monitoring during isotretinoin treatment for acne. According to Park and colleagues, it is advisable to monitor the levels of triglycerides, alanine aminotransferase, and aspartate aminotransferase every 5 to 6 months. Additionally, the levels of total cholesterol and low-density lipoprotein should be checked within the first two months of treatment. Isotretinoin is a commonly prescribed agent mainly used to treat acne. Despite its high effectiveness, it necessitates regular monitoring of laboratory parameters due to its side effect profile. Currently, there remains a lack of consensus on the appropriate frequency for monitoring these parameters during treatment with isotretinoin. This letter will provide insight into this complex and controversial topic. Based on existing literature, we concluded that the incidence of changes in lipid and liver aminotransferase levels during isotretinoin treatment for acne was low and likely clinically insignificant. For generally healthy people, we recommend testing lipid and liver profiles once at baseline and a second time at the peak dosage. However, frequent testing might still be beneficial in certain populations of patients.

3.
Clin Cosmet Investig Dermatol ; 17: 2373-2379, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39469661

RESUMEN

Purpose: Dyschromatosis symmetrica hereditaria (DSH) is a rare autosomal dominant inherited pigmentary dermatosis. The gene responsible for DSH has been identified as adenosine deaminase acting on RNA1 (ADAR1). This study aimed to identify the causative variants in the ADAR1 gene in three Chinese families with DSH. Patients and Methods: Data and blood samples were collected from three Chinese families with DSH. Whole-exome and Sanger sequencing were performed to detect pathogenic gene mutation in the patients. Bioinformatics tools were used to predict the pathogenicity of the variants. Results: Four heterozygous ADAR1 variants were identified, including two novel missense variants c.2369G>C (Arg790Pro), and 503C>T (Pro168Leu), and two previously reported variants: c.3232C>T(R1078C), and c.1472C>G (p.S491X). The novel c.503C>T variant was predicted as "deleterious" (score =-2.704) by PROVEAN, and "probably damaging" (score = 1) by PolyPhen2. The other novel variant c.2369G>C was also predicted as "deleterious" (score =-4.167) by PROVEAN, "probably damaging" (score = 1) by PolyPhen2, and "disease-causing" (p = 0.999) by Mutation Taster. Conclusion: Two novel ADAR1 variants were found in Chinese patients with DSH. This research has expanded the ADAR1 gene database for DSH, enhancing our comprehension of the underlying mechanisms.

4.
JACS Au ; 4(9): 3413-3420, 2024 Sep 23.
Artículo en Inglés | MEDLINE | ID: mdl-39328756

RESUMEN

The formation of a hexagonal diamond represents one of the most intriguing questions in materials science. Under shock conditions, the graphite basal plane tends to slide and pucker to form diamond. However, how the shock strength determines the phase selectivity remains unclear. In this work, using a DFT-trained carbon global neural network model, we studied the shock-induced graphite transition. The poor sliding caused by scarce sliding time under high-strength shock leads to metastable hexagonal diamond with an orientation relationship of (001)G//(100)HD+[010]G//[010]HD, while under low-strength shock due to long sliding distance cubic diamond forms with the orientation (001)G//(111)CD+[100]G//[110]CD, unveiling the strength-dependent graphite transition mechanism. We for the first time provide computational evidence of the strength-dependent graphite transition from first-principles, clarifying the long-term unresolved shock-induced hexagonal diamond formation mechanism and the structural source of the strength-dependent trend, which facilitates the hexagonal diamond synthesis via controlled experiment.

5.
Drug Des Devel Ther ; 18: 4003-4016, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39258275

RESUMEN

Background: Acne vulgaris (AV), a chronic inflammatory pilosebaceous disorder, affects 80-90% of teenagers. This study aimed to discover lipid profiles and biomarkers of the rabbit ear acne model, and investigate the mechanism of isotretinoin in treating acne at the lipid level. Methods: Untargeted lipidomic analysis using ultra-high performance liquid chromatography system (UHPLC) coupled to q-extraction plus was performed to identify skin lipid metabolites in blank control (groups C), model group (group M) and isotretinoin group (group T). Multivariate statistical analysis was used to process the lipidomics data. Results: A total of 43 lipid classes comprising 6989 lipid species were identified from the mass spectrometry data. The orthogonal partial least squares discriminant analysis (OPLS-DA) model demonstrated significant separation in skin lipidomic profiles between group M and group C. With variable influence on projection (VIP) > 1.0 and P-value < 0.05, 299 significantly different lipid metabolites were identified. These lipid metabolites consisted mainly of ceramides (Cer) (53.85%), phosphatidylethanolamines (PE) (9.03%), phosphatidylcholines (PC)(5.35%), and sphingomyelin (SM)(4.01%). Combining with AUC ≥ 0.9 as the elected criteria, Cer (d18;1_24:0), zymosterol (ZyE)(33:5), Cer (t43:1), ZyE (33:6), ZyE (24:7), and ZyE (35:6) have "high" accuracy. Isotretinoin treatment normalized 25 lipid metabolites in the acne model. Conclusion: Our findings provide new insights into the role of lipid metabolism in the pathogenesis of acne and the action mechanism of isotretinoin.


Asunto(s)
Acné Vulgar , Biomarcadores , Modelos Animales de Enfermedad , Isotretinoína , Lipidómica , Lípidos , Isotretinoína/farmacología , Acné Vulgar/tratamiento farmacológico , Acné Vulgar/metabolismo , Animales , Conejos , Biomarcadores/metabolismo , Biomarcadores/análisis , Lípidos/análisis , Cromatografía Líquida de Alta Presión , Masculino , Fármacos Dermatológicos/farmacología , Fármacos Dermatológicos/uso terapéutico
6.
Phys Chem Chem Phys ; 26(33): 22182-22188, 2024 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-39129444

RESUMEN

In this study, we report a novel monoclinic phase of carbon that contains 4+5+6+7+8 member rings in P21/m symmetry, identified by applying the stochastic surface walking method combined with high dimensional neural network potentials. We demonstrate that this phase possesses lower energy than graphite above 21.5 GPa. The phonon spectra show that this structure is stable under ambient pressure. This phase is a super hard material with a shear hardness as high as 81.9 GPa while it possesses an indirect band gap of 3.16 eV. The energy barrier of graphite to the Y phase is 0.27 eV, slightly higher than that of the hexagonal diamond (0.21 eV) in a similar phase transition mechanism. Two types of thermodynamically stable interfaces can be formed with the hexagonal diamond (HD), namely (001)Y//(100)HD, [100]Y//[010]HD and (001)Y//(001)HD, [010]Y//[001]HD. Although the discrete bulk Y phase is hard to synthesize, a faulted structure between HD is possible because of the well-matched interface between Y and HD. Our work shows that the Y phase may be formed in some special conditions and enhances our understanding of the formation of novel carbon allotropes.

7.
Int Braz J Urol ; 50(6): 727-736, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39133792

RESUMEN

INTRODUCTION: We aim to compare the safety and effectiveness of the KangDuo (KD)-Surgical Robot-01 (KD-SR-01) system and the da Vinci (DV) system for robot-assisted radical nephroureterectomy (RARNU). MATERIALS AND METHODS: This multicenter prospective randomized controlled trial was conducted between March 2022 and September 2023. Group 1 included 29 patients undergoing KD-RARNU. Group 2 included 29 patients undergoing DV-RARNU. Patient demographic and clinical characteristics, perioperative data, and follow-up outcomes were collected prospectively and compared between the two groups. RESULTS: There were no significant differences in patient baseline demographic and preoperative characteristics between the two groups. The success rates in both groups were 100% without conversion to open or laparoscopic surgery or positive surgical margins. No significant difference was observed in docking time [242 (120-951) s vs 253 (62-498) s, P = 0.780], console time [137 (55-290) min vs 105 (62-220) min, P = 0.114], operative time [207 (121-460) min vs 185 (96-305) min, P = 0.091], EBL [50 (10-600) mL vs 50 (10-700) mL, P = 0.507], National Aeronautics and Space Administration Task Load Index scores, and postoperative serum creatinine levels between the two groups. None of the patients showed evidence of distant metastasis, local recurrence, or equipment-related adverse events during the four-week follow-up. One (3.4%) patient in Group 2 experienced postoperative enterovaginal and enterovesical fistulas (Clavien-Dindo grade III). CONCLUSIONS: The KD-SR-01 system is safe and effective for RARNU compared to the DV Si or Xi system. Further randomized controlled studies with larger sample sizes and longer durations are required.


Asunto(s)
Nefroureterectomía , Tempo Operativo , Procedimientos Quirúrgicos Robotizados , Humanos , Procedimientos Quirúrgicos Robotizados/métodos , Procedimientos Quirúrgicos Robotizados/instrumentación , Femenino , Masculino , Estudios Prospectivos , Persona de Mediana Edad , Nefroureterectomía/métodos , Anciano , Resultado del Tratamiento , Neoplasias Renales/cirugía , Tiempo de Internación , Laparoscopía/métodos , Laparoscopía/instrumentación , Reproducibilidad de los Resultados , Complicaciones Posoperatorias
8.
Small ; 20(30): e2311161, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38456389

RESUMEN

The search for new phases is an important direction in materials science. The phase transition of sulfides results in significant changes in catalytic performance, such as MoS2 and WS2. Cubic pentlandite [cPn, (Fe, Ni)9S8] can be a functional material in batteries, solar cells, and catalytic fields. However, no report about the material properties of other phases of pentlandite exists. In this study, the unit-cell parameters of a new phase of pentlandite, sulfur-vacancy enriched hexagonal pentlandite (hPn), and the phase boundary between cPn and hPn are determined for the first time. Compared to cPn, the hPn shows a high coordination number, more sulfur vacancies, and high conductivity, which result in significantly higher hydrogen evolution performance of hPn than that of cPn and make the non-nano rock catalyst hPn superior to other most known nanosulfide catalysts. The increase of sulfur vacancies during phase transition provides a new approach to designing functional materials.

9.
Nat Commun ; 14(1): 6125, 2023 Sep 30.
Artículo en Inglés | MEDLINE | ID: mdl-37777546

RESUMEN

Defects passivation is widely devoted to improving the performance of formamidinium lead triiodide perovskite solar cells; however, the effect of various defects on the α-phase stability is still unclear. Here, using density functional theory, we first reveal the degradation pathway of the formamidinium lead triiodide perovskite from α to δ phase and investigate the effect of various defects on the energy barrier of phase transition. The simulation results predict that iodine vacancies are most likely to trigger the degradation, since they obviously reduce the energy barrier of α-to-δ phase transition and have the lowest formation energies at the perovskite surface. A water-insoluble lead oxalate compact layer is introduced on the perovskite surface to largely suppress the α-phase collapse through hindering the iodine migration and volatilization. Furthermore, this strategy largely reduces the interfacial nonradiative recombination and boosts the efficiency of the solar cells to 25.39% (certified 24.92%). Unpackaged device can maintain 92% of its initial efficiency after operation at maximum power point under simulated air mass 1.5 G irradiation for 550 h.

10.
Sci Adv ; 9(35): eadh3784, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37656794

RESUMEN

Water in Earth's deep interior is predicted to be hydroxyl (OH-) stored in nominally anhydrous minerals, profoundly modulating both structure and dynamics of Earth's mantle. Here, we use a high-dimensional neuro-network potential and machine learning algorithm to investigate the weight percent water incorporation in stishovite, a main constituent of the subducted oceanic crust. We found that stishovite and water prefer forming medium- to long-range ordered superstructures, featuring one-dimensional (1D) water channels. Synthesizing single crystals of hydrous stishovite, we verified the ordering of OH- groups in the water channels through optical and nuclear magnetic resonance spectroscopy and found an average H-H distance of 2.05(3) Å, confirming simulation results. Upon heating, H atoms were predicted to behave fluid-like inside the channels, leading to an exotic 1D superionic state. Water-bearing stishovite could feature high ionic mobility and strong electrical anisotropy, manifesting as electrical heterogeneity in Earth's mantle.

11.
Small ; 19(29): e2207295, 2023 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-37029585

RESUMEN

Tungsten oxide (WO3 ) is an appealing electrocatalyst for the hydrogen evolution reaction (HER) owing to its cost-effectiveness and structural adjustability. However, the WO3 electrocatalyst displays undesirable intrinsic activity for the HER, which originates from the strong hydrogen adsorption energy. Herein, for effective defect engineering, a hydrogen atom inserted into the interstitial lattice site of tungsten oxide (H0.23 WO3 ) is proposed to enhance the catalytic activity by adjusting the surface electronic structure and weakening the hydrogen adsorption energy. Experimentally, the H0.23 WO3 electrocatalyst is successfully prepared on reduced graphene oxide. It exhibits significantly improved electrocatalytic activity for HER, with a low overpotential of 33 mV to drive a current density of 10 mA cm-2 and ultra-long catalytic stability at high-throughput hydrogen output (200 000 s, 90 mA cm-2 ) in acidic media. Theoretically, density functional theory calculations indicate that strong interactions between interstitial hydrogen and lattice oxygen lower the electron density distributions of the d-orbitals of the active tungsten (W) centers to weaken the adsorption of hydrogen intermediates on W-sites, thereby sufficiently promoting fast desorption from the catalyst surface. This work enriches defect engineering to modulate the electron structure and provides a new pathway for the rational design of efficient catalysts for HER.

12.
IUCrJ ; 9(Pt 2): 253-260, 2022 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-35371496

RESUMEN

A series of in situ synchrotron X-ray diffraction (XRD) measurements were carried out, combined with first-principles calculations, to study structural phase transitions of selenium at high pressures and room temperature. Several phase transitions were observed, among which an isostructural phase transition was found at around 120 GPa for the first time. Evolved from the rhombohedral (space group R 3 m) structure (Se-V), the new phase (Se-V') exhibited an interesting increase of lattice parameter a at pressures from 120 to 148 GPa, known as negative linear compressibility (NLC). The discovery of NLC behavior observed in this work is mainly attributed to the accuracy and fine steps controlled by the membrane system for in situ XRD data collected with an exposure time of 0.5 s. After 140 GPa, a body-centered cubic (b.c.c.) structure Se-VI (space group Im 3 m) was formed, which remains stable up to 210 GPa, the highest pressure achieved in this study. The bulk moduli of phases Se-V, Se-V' and Se-VI were estimated to be 83 ± 2, 321 ± 2 and 266 ± 7 GPa, respectively, according to the P-V curve fit by the third-order Birch-Murnaghan equation of state. The Se-V' phase shows a bulk modulus almost 4 times larger than that of the Se-V phase, which is mainly due to the effect of its NLC. NLC in a higher pressure range is always more significant in terms of fundamental mechanism and new materials discovery, yet it has barely been reported at pressures above 100 GPa. This will hopefully inspire future studies on potential NLC behaviors in other materials at ultra-high pressure.

13.
J Am Chem Soc ; 144(16): 7414-7421, 2022 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-35420809

RESUMEN

Identifying ordering in non-crystalline solids has been a focus of natural science since the publication of Zachariasen's random network theory in 1932, but it still remains as a great challenge of the century. Literature shows that the hierarchical structures, from the short-range order of first-shell polyhedra to the long-range order of translational periodicity, may survive after amorphization. Here, in a piece of AlPO4, or berlinite, we combine X-ray diffraction and stochastic free-energy surface simulations to study its phase transition and structural ordering under pressure. From reversible single crystals to amorphous transitions, we now present an unambiguous view of the topological ordering in the amorphous phase, consisting of a swarm of Carpenter low-symmetry phases with the same topological linkage, trapped in a metastable intermediate stage. We propose that the remaining topological ordering is the origin of the switchable "memory glass" effect. Such topological ordering may hide in many amorphous materials through disordered short atomic displacements.

14.
Phys Chem Chem Phys ; 24(11): 7007-7013, 2022 Mar 16.
Artículo en Inglés | MEDLINE | ID: mdl-35254347

RESUMEN

Scandium (Sc) is the lightest non-main-group element and transforms to a host-guest (H-G) incommensurate structure under gigapascal (GPa) pressures. While the host structure is stable over a wide pressure range, the guest structure may exist in multiple forms, featuring different incommensurate ratios, and mixing up to generate long-range "disordered" guest structures. Here, we employed the recently developed global neural network (g-NN) potential and the stochastic surface walking (SSW) global optimization algorithm to explore the global potential energy surface of Sc under various pressures. We probe the global minima structure in a system made of hundreds of atoms and revealed that the solid-phase transition between Sc-I and H-G Sc-II phases is fully reconstructive in nature. Above 62.5 GPa, the pressure will further destabilize the face-centered tetragonal (fct, Sc-IIa) guest structure to a body-centered tetragonal phase (bct, Sc-IIb), while sustaining the host structure. The structural transition mechanism of this work will shed light on the nature of the complex H-G structural modifications in compressed metals.

15.
J Phys Chem Lett ; 12(45): 10996-11004, 2021 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-34739250

RESUMEN

Tin halide perovskite's potential as a photovoltaic absorber has not been fully realized to date, largely due to its instability in ambient air. Here, we demonstrate by both experiments and simulations that the air instability of black-phase cesium tin iodide perovskite (γ-CsSnI3) could be greatly lessened by a controlled incorporation of bismuth (Bi) ions into the crystal lattice. Hall effect measurements on films of γ-CsSnI3 suggest the unwanted formation of a tin vacancy and p-type self-doping can be effectively suppressed by the Bi incorporation. Structural and optical results indicate that the Bi incorporation markedly enhances the air stability by impeding the direct conversion of γ-CsSnI3 to zero-dimensional Cs2SnI6. By using a stochastic surface walking (SSW) method integrating neural network (NN) potential and density functional theory (DFT), it is revealed that the remarkable enhanced stability could be attributed to a combination of factors originating from lattice-contraction-induced strain, a suppressed tin vacancy, and an increased energy barrier for the transformation of γ-CsSnI3 to Cs2SnI6. This study provides physical insights into the stabilization mechanism of tin perovskites by heterovalent B-site engineering, paving the way for realizing stable and efficient lead-free perovskite photovoltaics.

16.
Phys Chem Chem Phys ; 23(36): 20560-20566, 2021 Sep 22.
Artículo en Inglés | MEDLINE | ID: mdl-34505586

RESUMEN

The discovery of graphite transition to transparent and superhard carbons under room-temperature compression (Takehiko, et al., Science, 1991, 252, 1542 and Mao, et al., Science, 2003, 302, 425) launched decades of intensive research into carbon's structural polymorphism and relative phase transition mechanisms. Although many possible carbon allotropes have been proposed, experimental observations and their transition mechanisms are far from conclusive. Three longstanding issues are: (i) the speculative structures inferred by amorphous-like XRD peaks, (ii) sp2 and sp3 bonding mixing, and (iii) the controversies of transition reversibility. Here, by utilizing the stochastic surface walking method for unbiased pathway sampling, we resolve the possible atomic structure and the lowest energy pathways between multiple carbon allotropes under high pressure. We found that a new transition pathway, through which graphite transits to a highly disordered phase by shearing the boat architecture line atoms out of the graphite (001) plane upward or downward featuring without the nuclei core, is the most favorable. This transition pathway facilitates the generation of a variety of equally favorable carbon structures that are controlled by the local strain and crystal orientation, resembling structural disordering. Our results may help to understand the nature of graphite under room temperature compression.

17.
Int J Surg ; 75: 165-173, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31978650

RESUMEN

OBJECTIVES: To assess the oncological outcomes of several distal ureter management techniques in patients administered with radical nephroureterectomy (RNU) for primary upper urinary tract urothelial carcinoma (UTUC). METHODS: A systematic search of PubMed, EMBASE, and the Cochrane Library was conducted to identify studies comparing outcomes following RNU under various surgical methods for bladder cuff management. Standard cumulative analyses of hazard ratios (HRs) with 95% confidence intervals (CIs) were performed using Review Manager (5.3). RESULTS: Nine studies involving 4683 patients were selected based upon eligibility criteria. Meta-analysis of cancer-specific survival (CSS) and overall survival (OS) revealed no significant differences among intravesical incision of the bladder cuff (IVBC), extravesical incision of the bladder cuff (EVBC) and transurethral incision of the bladder cuff (TUBC) techniques. However, the IVBC technique appeared to have better recurrence-free survival (RFS) (HR = 1.37, p < 0.01) and intravesical recurrence-free survival (IRFS) (HR = 1.45, p < 0.01) compared with non-IVBC methods, including both TUBC and EVBC. When studies involving patients with bladder tumour history were excluded, the pooled statistic appeared to confirm that IVBC was associated with improved IRFS (HR = 1.25, p = 0.03) compared with EVBC and TUBC. No significant difference was found between the EVBC and TUBC groups (HR = 1.81, p = 0.32). CONCLUSIONS: The findings suggest that IVBC is associated with improved oncologic outcomes and that it may be recommended for distal ureter management. However, caution must be taken because this recommendation is based upon a very limited number of clinical studies. Further research with enhanced outcome data collection and improved reporting is required to confirm these findings.


Asunto(s)
Nefroureterectomía/métodos , Uréter/cirugía , Neoplasias Urológicas/cirugía , Humanos , Estudios Retrospectivos , Neoplasias Urológicas/mortalidad
18.
J Vis Exp ; (153)2019 11 22.
Artículo en Inglés | MEDLINE | ID: mdl-31814624

RESUMEN

Upper tract urothelial carcinoma (UTUC) accounts for 5%-10% of all urothelial tumors. Radical nephroureterectomy is the standard treatment procedure. At present, different choices still exist for treating the ureteral end during laparoscopic ureteral bladder sleeve resection. Our center has adopted a new method for treating the ureteral end. This new method can increase the operating space and reduce the difficulty of the surgery compared with current methods.


Asunto(s)
Laparoscopía/métodos , Nefroureterectomía/instrumentación , Uréter/cirugía , Neoplasias Ureterales/cirugía , Anciano , Carcinoma de Células Transicionales , Humanos , Persona de Mediana Edad , Nefroureterectomía/métodos , Estudios Retrospectivos , Vejiga Urinaria/cirugía
19.
ACS Appl Mater Interfaces ; 11(5): 5256-5263, 2019 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-30644709

RESUMEN

Electrides are a class of materials which contain excess electrons occupying the cavities in the crystal and playing the role of anions. To achieve electron-rich conditions, it usually requires a positive total formal charge in electride materials. However, the assignment of charges relies on a detailed analysis on chemical bonding. Herein, we present a survey on potential electrides which may be overlooked if no bonding analysis is performed. By applying various structure sampling techniques in conjunction with first-principles calculation, we predicted two compounds Ba2N2:e- and Li2Ca3N6:2e-, both of which are featured by the presence of dinitrogen ligands [N2], to be potential electrides. While Li2Ca3N6:2e- with [N2]2- ions has been synthesized in the past, its electride nature was discovered for the first time based on our high-throughput screening. On the other hand, Ba2N2:e- with [N2]3- ions is a new compound entirely from first-principles structure prediction. The different valence states of dinitrogen ligands identified in these two compounds suggest a novel route to tune the concentration and anisotropic properties of anionic interstitial electrons. Our discovery does not only establish a new class of inorganic electrides but also demonstrates the predictive power of modern crystal structure sampling techniques toward rational material design.

20.
Inorg Chem ; 58(9): 5476-5482, 2019 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-30556389

RESUMEN

Solid-solid reaction, particularly in the Fe-O binary system, has been extensively studied in the past decades because of its various applications in chemistry and materials and earth sciences. The recently synthesized pyrite-FeO2 at high pressure suggested a novel oxygen-rich stoichiometry that extends the achievable O-Fe ratio in iron oxides by 33%. Although FeO2 was synthesized from Fe2O3 and O2, the underlying solid reaction mechanism remains unclear. Herein, combining in situ X-ray diffraction experiments and first-principles calculations, we identified that two competing phase transitions starting from Fe2O3: (1) without O2, perovskite-Fe2O3 transits to the post-perovskite structure above 50 GPa; (2) if free oxygen is present, O diffuses into the perovskite-type lattice of Fe2O3 leading to the pyrite-type FeO2 phase. We found the O-O bonds in FeO2 are formed by the insertion of oxygen into the Pv lattice via the external stress and such O-O bonding is only kinetically stable under high pressure. This may provide a general mechanism of adding extra oxygen to previous known O saturated oxides to produce unconventional stoichiometries. Our results also shed light on how O is enriched in mantle minerals under pressure.

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