Engineering topics
Publications and source records attributed to Boldyrev, Alexander I..
This article explores the application of NN atomistic potentials, specifically ANI-1ccx and ANI-nr, for efficient global minima optimization in carbon clusters. Combined with the cluster distance restriction, they are robust PES pre-samplers.
Synthetic exploration and theoretical characterization of metal clusters are actively developing branches of modern inorganic chemistry. Advances in these areas constantly expand the rich structural diversity of viable species, allowing a detailed study of the fundamental characteristics of bench-stable compounds. In this minireview, we summarize recent achievements in synthesis and computational analyses of main-group and heterometallic clusters containing multiple aromatic/antiaromatic units. These systems range from bare clusters to ligand-decorated aggregates, providing a fundamental understanding of the aromaticity and antiaromaticity concepts in species exhibiting unprecedented shapes and composition. The review gives a comprehensive summary of bonding and magnetic response properties of such systems deciphered from the Adaptive Natural Density Partitioning (AdNDP) approach and induced magnetic field analyses.
Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M 2 (CO) 6 Sn 2 Sb 5 ] 3- (M = Cr, Mo), and [(MSn 2 Sb 5 ) 2 ] 4- , (M = Cu, Ag)) in the process of capturing the hypho - [Sn 2 Sb 5 ] 3- in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo 2 (CO) 6 Sn 2 Sb 5 ] 3- stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn 2 Sb 5 ) 2 ] 4- and [(CuSn 2 Sb 5 ) 2 ] 4- render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn 2 Sb 5 ] 3- , thus providing conceptual advances in the field of metal-metal bonding in clusters.
Machine learning (ML) is quickly becoming a premier tool for modeling chemical processes and materials. ML-based force fields, trained on large data sets of high-quality electron structure calculations, are particularly attractive due their unique combination of computational efficiency and physical accuracy. This Perspective summarizes some recent advances in the development of neural network-based interatomic potentials. Designing high-quality training data sets is crucial to overall model accuracy. One strategy is active learning, in which new data are automatically collected for atomic configurations that produce large ML uncertainties. Another strategy is to use the highest levels of quantum theory possible. Transfer learning allows training to a data set of mixed fidelity. A model initially trained to a large data set of density functional theory calculations can be significantly improved by retraining to a relatively small data set of expensive coupled cluster theory calculations. These advances are exemplified by applications to molecules and materials.
Abstract In this work, the largest heterometallic supertetrahedral clusters, [Zn 6 Ge 16 ] 4− and [Cd 6 Ge 16 ] 4− , were directly self‐assembled through highly‐charged [Ge 4 ] 4− units and transition metal cations, in which 3‐center–2‐electron σ bonding in Ge 2 Zn or Ge 2 Cd triangles plays a vital role in the stabilization of the whole structure. The cluster structures have an open framework with a large central cavity of diameter 4.6 Å for Zn and 5.0 Å for Cd, respectively. Time‐dependent HRESI‐MS spectra show that the larger clusters grow from smaller components with a single [Ge 4 ] 4− and ZnMes 2 units. Calculations performed at the DFT level indicate a very large HOMO–LUMO energy gap in [M 6 Ge 16 ] 4− (2.22 eV), suggesting high kinetic stability that may offer opportunities in materials science. These observations offer a new strategy for the assembly of heterometallic clusters with high symmetry.
Here, the largest heterometallic supertetrahedral clusters, [Zn 6 Ge 16 ] 4– and [Cd 6 Ge 16 ] 4– , were directly self-assembled through highly-charged [Ge 4 ] 4– units and transition metal cations, in which 3-center–2-electron σ bonding in Ge 2 Zn or Ge 2 Cd triangles plays a vital role in the stabilization of the whole structure. The cluster structures have an open framework with a large central cavity of diameter 4.6 Å for Zn and 5.0 Å for Cd, respectively. Time-dependent HRESI-MS spectra show that the larger clusters grow from smaller components with a single [Ge 4 ] 4– and ZnMes 2 units. Calculations performed at the DFT level indicate a very large HOMO–LUMO energy gap in [M 6 Ge 16 ] 4– (2.22 eV), suggesting high kinetic stability that may offer opportunities in materials science. These observations offer a new strategy for the assembly of heterometallic clusters with high symmetry.
Until now, all B≡B triple bonds have been achieved by adopting two ligands in the L→B≡B←L manner. Herein, we report an alternative route of designing the B≡B bonds based on the assumption that by acquiring two extra electrons, an element with the atomic number Z can have properties similar to those of the element with the atomic number Z + 2. Specifically, we show that due to the electron donation from Al to B, the negatively charged B≡B kernel in the B 2 Al 3 – cluster mimics a triple N≡N bond. Comprehensive computational searches reveal that the global minimum structure of B 2 Al 3 – exhibits a direct B–B distance of 1.553 Å, and its calculated electron vertical detachment energies are in excellent agreement with the corresponding values of the experimental photoelectron spectrum. Chemical bonding analysis revealed one σ and two π bonds between the two B atoms, thus confirming a classical textbook B≡B triple bond, similar to that of N 2 .
Abstract We report the characterization of the compound [K([2.2.2]crypt)] 4 [In 8 Sb 13 ], which proves to contain a 1:1 mixture of [Sb@In 8 Sb 12 ] 3− and [Sb@In 8 Sb 12 ] 5− . The tri‐anion displays perfect T h symmetry, the first completely inorganic molecule to do so, and contains eight equivalent In 3+ centers in a cube. The gas‐phase potential energy surface of the penta‐anion has eight equivalent minima where the extra pair of electrons is localized on one In + center, and these minima are linked by low‐lying transition states where the electron pair is delocalized over two adjacent centers. The best fit to the electron density is obtained from a model where the structure of the 5− cluster lies close to the gas‐phase transition state.
We report the characterization of the compound [K([2.2.2]crypt)] 4 [In 8 Sb 13 ], which proves to contain a 1:1 mixture of [Sb@In 8 Sb 12 ] 3– and [Sb@In 8 Sb 12 ] 5– . The tri–anion displays perfect T h symmetry, the first completely inorganic molecule to do so, and contains eight equivalent In 3+ centers in a cube. The gas–phase potential energy surface of the penta–anion has eight equivalent minima where the extra pair of electrons is localized on one In+ center, and these minima are linked by low–lying transition states where the electron pair is delocalized over two adjacent centers. In conclusion, the best fit to the electron density is obtained from a model where the structure of the 5– cluster lies close to the gas–phase transition state.
We report the discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry. A classical triple bond such as N≡N and HC≡CH contains one σ bond and two π bonds constructed from the p orbitals perpendicular to the σ bond. However, the traditional textbook triple bond between two Al atoms has remained elusive. Here we report an Al≡Al triple bond in the designer Na 3 Al 2 - cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations. Being effectively Al 2- due to the electron donation from Na, the Al atoms in Na 3 Al 2 - undergo a double electronic transmutation into Group 15 elements, thus the Al 2- ≡Al 2- kernel mimics the P≡P and N≡N molecules. Lastly, we anticipate this work will stimulate more endeavors in discovering materials using Al 2- ≡Al 2- as a building block in the gas phase and in the solid state.
Originally, the concepts of aromaticity and antiaromaticity were introduced to explain the stability and reactivity of unsaturated organic compounds. Since then, they have been extended to other species with delocalized electrons including various saturated systems, organometallic compounds, and even inorganic clusters and molecules. In this study, we focus on the most recent progress of using these concepts to guide experimental synthesis and rationalize geometrical and electronic structures of a particular family of polyanions composed of Group 14 and 15 elements, namely Zintl clusters.
Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, using the ab initio evolutionary algorithm USPEX and subsequent high-pressure synthesis in a diamond anvil cell, we report the discovery of a thermodynamically stable compound of helium and sodium, Na 2 He, which has a fluorite-type structure and is stable at pressures >113 GPa. We show that the presence of He atoms causes strong electron localization and makes this material insulating. This phase is an electride, with electron pairs localized in interstices, forming eight-centre two-electron bonds within empty Na 8 cubes. As a result, we also predict the existence of Na 2 HeO with a similar structure at pressures above 15 GPa.