Georgiy Akopov

Rutgers, The State University of New Jersey | Rutgers · Department of Chemistry (Newark)

Transition-metal phosphides (TMP) have been identified as promising electrocatalysts for the hydrogen evolution reaction (HER). Despite recent computational investigations identifying P sites as being crucial for hydrogen adsorption, the main mode of optimization for TMPs has been focused on changing the metal sites. To experimentally verify comput...

Noncentrosymmetric (NCS) silicon phosphides have recently shown promise as nonlinear optical materials due to the balance of strong second harmonic generation (SHG) activity and large laser damage threshold (LDT) values....

Non-centrosymmetric semiconductors may exhibit non-linear optical (NLO) properties. For the application-relevant materials a careful balance of high second-harmonic generation (SHG) and high laser damage threshold (LDT) as well as phase-matchability...

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 greatl...

Non‐linear optical materials must possess a balanced combination of laser‐induced damage threshold (LDT) and second‐harmonic generation (SHG) and be phase matchable. In our previous work, chiral and polar La3CuGeS7 was identified as promising non‐linear optical material. Herein, we report the optimization of non‐linear optical properties through re...

Non-linear optical (NLO) materials require a balance of high second-harmonic generation (SHG) signal and laser damage threshold (LDT), as well as phase matchable behavior. Herein, we report a new member of the (RE)6(TM)x(Tt)2Q14 family of compounds, La6PdSi2S14, which, unlike all other reported TM analogues crystallizing in hexagonal P63 space grou...

Centrosymmetric skutterudite RhP3 was converted to a nonsymmorphic and chiral compound RhSi0.3P2.7 (space group P212121) by means of partial replacement of Si for P. The structure, determined by a combination of X‐ray crystallography and solid state 31P NMR, exhibits branched polyanionic P/Si chains that are unique among metal phosphides. A driving...

An innovative method of synthesis is reported for the large and diverse (RE)6(TM) x (Tt)2S14 (RE = rare-earth, TM = transition metals, Tt = Si, Ge, and Sn) family of compounds (∼1000 members, ∼325 contain Si), crystallizing in the noncentrosymmetric, chiral, and polar P63 space group. Traditional synthesis of such phases involves the annealing of e...

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...

Compared to common types of Au(I) coordination, such as linear, trigonal planar, and tetrahedral units observed in extended solids, the square planar coordination is rare. Au(I)relia, shown in the cover image, exhibits the 3‐centered bonding of Au‐Tt‐Au and Au‐Pn‐Au (on her feathers), square planar cis‐[AuTt2Pn2] units (her pendant), and linear …‐A...

Materials with superior hardness can be categorized as ultrahard (Vickers hardness, Hv ≥ 80 GPa) and superhard (Hv ≥ 40 GPa). These materials are commonly used as cutting tools and abrasives in the machining and manufacturing industries. With its extreme hardness, diamond is the best known and most used ultrahard material for industrial application...

Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal‐rich silicon phosphides RuSi4P4 and IrSi3P3 are synthesized and characterized. Their crystal structures are reinvestigated usin...

Three novel isostructural equiatomic gold tetrel pnictides, AuSiAs, AuGeP, and AuGeAs, were synthesized and characterized. These phases crystallize in the noncentrosymmetric (NCS) monoclinic space group Cc (No. 9), featuring square planar Au within cis -[AuTt 2 Pn 2 ] units ( Tt = tetrel, Si, Ge; Pn = pnictogen, P, As). This is in drastic contrast...

La 2 SiP 4 ( mP ‐28, Z = 4, Wyckoff sequence e 7 , space group P 2 1 / c (No. 14), a = 10.8230(6) Å, b = 7.5208(4) Å, c = 7.9189(4) Å, and β = 105.389(2) o ) which crystallizes in the La 2 CuS 4 structure type is reported. Instead of isolated CuS 3 triangles bridged by disulfide anions, in the crystal structure of La 2 SiP 4 , one‐dimensional zig‐z...

Single-phase metal dodecaboride (MB12) solid solutions, Zr0.5Y0.5B12 and Zr0.5U0.5B12 were prepared by arc melting from the pure elements. The phase purity and composition were established by powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and ¹⁰B and ¹¹B solid-state nuclear magnet...

The deformation behavior of the three metal dodecaborides (YB12, ZrB12, and Zr0.5Y0.5B12) is investigated using radial X‐ray diffraction under nonhydrostatic compression up to ≈60 GPa with a goal of understanding how bonding and metal composition control hardness. Zr0.5Y0.5B12, which has the highest Vickers hardness (Hv = 45.8 ± 1.3 GPa at 0.49 N l...

Solid solutions of tungsten diboride (WB2) with increasing substitution of tungsten (W) by tantalum (Ta) and niobium (Nb) - ranging from 0 to 50 at. % on a metals basis - were synthesized through resistive arc melting. Samples were characterized using a combination of powder X-ray diffraction (PXRD) for phase identification, energy-dispersive X-ray...

Metal borides of the YCrB4, Y2ReB6, Y3ReB7 and YMo3B7 structural types, and their solid-solutions were analyzed using powder X-ray diffraction and energy-dispersive X-ray spectroscopy, and studied for their mechanical properties. These metal borides possess unique crystal structures, not found in any other type of borides: alternating metal and bor...

Previous efforts toward the synthesis of materials with superior mechanical properties (e.g., superhardness, high bulk modulus, and high shear modulus) have focused on binary metal boride structures with short covalent bonds. In this paper, we discuss the methods for enhancing the intrinsic and extrinsic hardening factors commonly used to achieve t...

Tungsten tetraboride (WB4) solid-solutions with Y, Sc, Gd, Tb, Dy, Ho and Er were prepared by arc-melting and investigated for their thermal stability and mechanical properties. The phase composition and purity were confirmed by powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS). In all cases, except for Sc, a change to...

Samples of metal borides with a nominal composition of ((M1)(1-x-z)(M2)(x)(M3)(z)) : 20B (M1, M2 and M3 = Zr, Y, Hf and Gd) were prepared by arc-melting and studied for phase composition (using powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS)) and mechanical properties (Vickers hardness). Ternary metal dodecaborides ph...

Tungsten tetraboride is an inexpensive, superhard material easily prepared at ambient pressure. Unfortunately, there are relatively few compounds in existence that crystallize in the same structure as tungsten tetraboride. Furthermore, the lack of data in the tetraboride phase space limits the discovery of any new superhard compounds that also poss...

Polyaniline is known for reversible acidic doping. However, despite extensive work, little experimental evidence exists for the initial doping mechanism mainly due to the difficulty of synthesizing polyaniline with a uniform chain length. In this study, we partially dope aniline tetramers in order to investigate the initial stage of doping in both...

For decades, borides have been primarily studied as crystallographic oddities. With such a wide variety of structures (a quick survey of the Inorganic Crystal Structure Database counts 1253 entries for binary boron compounds!), it is surprising that the applications of borides have been quite limited despite a great deal of fundamental research. If...

We report ambient pressure stabilization of a previously synthesized high-pressure (6.5 GPa) phase, GdB12, in a Zr1-xGdxB12 solid solution (with ∼54 at. % Gd solubility, as determined by both powder X-ray diffraction and energy-dispersive spectroscopy). Limited solubilities of Sm (∼15 at. % Sm), Nd (∼7 at. % Nd), and Pr (∼4 at. % Pr), in ZrB12 were...

The primary focus of superhard materials development has relied on chemical tuning of the crystal structure. While these intrinsic effects are invaluable, there is a strong possibility that hardness can be dramatically enhanced using extrinsic effects. Here, we demonstrate that the superhard metal W0.5 Ta 0.5B can be prepared as nanowires through f...

The solid solutions Zr1-xYxB12, Zr1-xScxB12, and Y1-xScxB12 (x = 0—1) as well as ScB50 and YB66 are prepared by arc-melting of the elements in ratios of 1:20 for the dodecaborides and 1:65 and 1:70 for the latter two binary phases.

Solid solutions of mixed metal dodecaborides of ZrB12, YB12, and ScB12 were prepared by arc-melting and studied for their mechanical properties. Zr1-xYxB12 formed an essentially perfect solid solution, closely following Vegard's law. Zr1-xScxB12 and Y1-xScxB12 undergo a face centered-cubic to body-centered tetragonal transition at 90-95 at. % Sc as...

The high-pressure HfB12 phase is stabilized in the Y1-xHfxB12 (x = 0.00, 0.05, 0.25, 0.50, 0.75, 0.95) system (obtained by arc-melting of the elements) under ambient pressure.

Alloys of tungsten tetraboride (WB4) with the group 4 transition metals, titanium (Ti), zirconium (Zr), and hafnium (Hf), of different concentrations (0–50 at. % on a metals basis) were synthesized by arc-melting in order to study their mechanical properties. The phase composition and purity of the as-synthesized samples were confirmed using powder...

Alloys of metal dodecaborides—YB12 with HfB12—were prepared via arc-melting in order to stabilize the metastable HfB12 high-pressure phase under ambient pressure. Previously, HfB12 had been synthesized only under high-pressure (6.5 GPa). Powder X-ray diffraction (PXRD) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the purity a...