Computational electron-phonon superconductivity: from theoretical physics to material science.

The search for room-temperature superconductors is a major challenge in modern physics. The discovery of copper-oxide superconductors in 1986 brought hope but also revealed complex mechanisms that are difficult to analyze and compute. In contrast, the traditional electron-phonon coupling (EPC) mechanism facilitated the practical realization of superconductivity (SC) in metallic hydrogen.

When van der Waals Met Kagome: A 2D Antimonide with a Vanadium-Kagome Network.

2D materials showcase unconventional properties emerging from quantum confinement effects. In this work, a "soft chemical" route allows for the deintercalation of K from the layered antimonide KVSb, resulting in the discovery of a new metastable 2D-Kagome antimonide KVSb with a van der Waals gap of 3.2 Å.

High-Throughput Screening for Boride Superconductors.

A high-throughput screening using density functional calculations is performed to search for stable boride superconductors from the existing materials database. The workflow employs the fast frozen-phonon method as the descriptor to evaluate the superconducting properties quickly. Twenty-three stable candidates were identified during the screening.

Structure, bonding and electronic characteristics of amorphous Se.

Ovonic threshold switching (OTS) selectors can effectively improve the storage density and suppress the leakage current of advanced phase-change memory devices. As a prototypical OTS material, amorphous GeSe is widely investigated. But the attention paid to amorphous Se (, the functional constituent in amorphous GeSe) has been very limited up to now.

Prediction of superconductivity in metallic boron-carbon compounds from 0 to 100 GPa by high-throughput screening.

Boron-carbon compounds have been shown to have feasible superconductivity. In our earlier paper [Zheng , , 2023, , 014508], we identified a new conventional superconductor of LiBC at 100 GPa. Here, we aim to extend the investigation of possible superconductivity in this structural framework by replacing Li atoms with 27 different cations from periods 3, 4, and 5 under pressures ranging from 0 to 100 GPa.

Ground and excited states of even-numbered Hubbard ring at half-filling: comparison of the extended Gutzwiller approach with exact diagonalization.

It remains a great challenge in condensed matter physics to develop a method to treat strongly correlated many-body systems with balanced accuracy and efficiency. We introduce an extended Gutzwiller (EG) method incorporating a manifold technique, which builds an effective manifold of the many-body Hilbert space, to describe the ground-state (GS) and excited-state (ES) properties of strongly correlated electrons. We systematically apply an EG projector onto the GS and ES of a non-interacting system.

Iron-rich Fe-O compounds at Earth's core pressures.

Oxygen and iron are the most abundant elements on Earth, and their compounds are key planet-forming components. While oxygen is pervasive in the mantle, its presence in the solid inner core is still debatable. Yet, this issue is critical to understanding the co-evolution and the geomagnetic field generation.

Accelerating the discovery of novel magnetic materials using machine learning-guided adaptive feedback.

Magnetic materials are essential for energy generation and information devices, and they play an important role in advanced technologies and green energy economies. Currently, the most widely used magnets contain rare earth (RE) elements. An outstanding challenge of notable scientific interest is the discovery and synthesis of novel magnetic materials without RE elements that meet the performance and cost goals for advanced electromagnetic devices.

High-Throughput Screening of Strong Electron-Phonon Couplings in Ternary Metal Diborides.

We perform a high-throughput screening on phonon-mediated superconductivity in a ternary metal diboride structure with alkali, alkaline earth, and transition metals. We find 17 ground states and 78 low-energy metastable phases. From fast calculations of zone-center electron-phonon coupling, 43 compounds are revealed to show electron-phonon coupling strength higher than that of MgB.

A rotationally invariant approach based on Gutzwiller wave function for correlated electron systems.

We introduce a rotationally invariant approach combined with the Gutzwiller conjugate gradient minimization method to study correlated electron systems. In the approach, the Gutzwiller projector is parametrized based on the number of electrons occupying the onsite orbitals instead of the onsite configurations. The approach efficiently groups the onsite orbitals according to their symmetry and greatly reduces the computational complexity, which yields a speedup of20∼50×in the minimal basis energy calculation of dimers.

Machine Learning-Guided Discovery of Ternary Compounds Containing La, P, and Group 14 Elements.

We integrate a deep machine learning (ML) method with first-principles calculations to efficiently search for the energetically favorable ternary compounds. Using La-Si-P as a prototype system, we demonstrate that ML-guided first-principles calculations can efficiently explore crystal structures and their relative energetic stabilities, thus greatly accelerate the pace of material discovery. A number of new La-Si-P ternary compounds with formation energies less than 30 meV/atom above the known ternary convex hull are discovered.

Path Less Traveled: A Contemporary Twist on Synthesis and Traditional Structure Solution of Metastable LiNiB.

Achieving kinetic control to synthesize metastable compounds is a challenging task, especially in solid-state reactions where the diffusion is slow. Another challenge is the unambiguous crystal structure determination for metastable compounds when high-quality single crystals suitable for single-crystal X-ray diffraction are inaccessible. In this work, we report an unconventional means of synthesis and an effective strategy to solve the crystal structure of an unprecedented metastable compound LiNiB.

The Gutzwiller conjugate gradient minimization method for correlated electron systems.

We review our recent work on the Gutzwiller conjugate gradient minimization method, anapproach developed for correlated electron systems. The complete formalism has been outlined that allows for a systematic understanding of the method, followed by a discussion of benchmark studies of dimers, one- and two-dimensional single-band Hubbard models. In the end, we present some preliminary results of multi-band Hubbard models and large-basis calculations of Fto illustrate our efforts to further reduce the computational complexity.

Two-step nucleation of the Earth's inner core.

The Earth's inner core started forming when molten iron cooled below the melting point. However, the nucleation mechanism, which is a necessary step of crystallization, has not been well understood. Recent studies have found that it requires an unrealistic degree of undercooling to nucleate the stable, hexagonal, close-packed (hcp) phase of iron that is unlikely to be reached under core conditions and age.

Lithium Diffusion in Silicon Encapsulated with Graphene.

The model of a graphene (Gr) sheet putting on a silicon (Si) substrate is used to simulate the structures of Si microparticles wrapped up in a graphene cage, which may be the anode of lithium-ion batteries (LIBS) to improve the high-volume expansion of Si anode materials. The common low-energy defective graphene (-Gr) structures of DV5-8-5, DV555-777 and SV are studied and compared with perfect graphene (-Gr). First-principles calculations are performed to confirm the stable structures before and after Li penetrating through the Gr sheet or graphene/Si-substrate (Gr/Si) slab.

Neural network potential for Zr-Rh system by machine learning.

Zr-Rh metallic glass has enabled its many applications in vehicle parts, sports equipment and so on due to its outstanding performance in mechanical property, but the knowledge of the microstructure determining the superb mechanical property remains yet insufficient. Here, we develop a deep neural network potential of Zr-Rh system by using machine learning, which breaks the dilemma between the accuracy and efficiency in molecular dynamics simulations, and greatly improves the simulation scale in both space and time. The results show that the structural features obtained from the neural network method are in good agreement with the cases inmolecular dynamics simulations.

How to Look for Compounds: Predictive Screening and in situ Studies in Na-Zn-Bi System.

Here, the combination of theoretical computations followed by rapid experimental screening and in situ diffraction studies is demonstrated as a powerful strategy for novel compounds discovery. When applied for the previously "empty" Na-Zn-Bi system, such an approach led to four novel phases. The compositional space of this system was rapidly screened via the hydride route method and the theoretically predicted NaZnBi (PbClF type, P4/nmm) and Na Zn Bi (Na Cd Sb type, P ) phases were successfully synthesized, while other computationally generated compounds on the list were rejected.

Ternary Zinc Antimonides Unlocked Using Hydride Synthesis.

Three new sodium zinc antimonides NaZnSb, NaZnSb, and NaZnSb were synthesized utilizing sodium hydride NaH as a reactive sodium source. In comparison to the synthesis using sodium metal, salt-like NaH can be ball-milled, leading to the easy and uniform mixing of precursors in the desired stoichiometric ratios. Such comprehensive compositional control enables a fast screening of the Na-Zn-Sb system and identification of new compounds, followed by their preparation in bulk with high purity.

Third time's the charm: intricate non-centrosymmetric polymorphism in SiP ( = La and Ce) induced by distortions of phosphorus square layers.

Complex polymorphic relationships in the LnSiP3 (Ln = La and Ce) family of compounds are reported. An innovative synthetic method was developed to overcome differences in the reactivities of the rare-earth metal and refractory silicon with phosphorus. Reactions of atomically mixed Ln + Si with P allowed for selective control over the reaction outcomes resulting in targeted isolation of three new polymorphs of LaSiP3 and two polymorphs of CeSiP3.

Topochemical Deintercalation of Li from Layered LiNiB: toward 2D MBene.

The pursuit of two-dimensional (2D) borides, MBenes, has proven to be challenging, not the least because of the lack of a suitable precursor prone to the deintercalation. Here, we studied room-temperature topochemical deintercalation of lithium from the layered polymorphs of the LiNiB compound with a considerable amount of Li stored in between [NiB] layers (33 at. % Li).