Journal of Computational Chemistry最新文献

Metal/graphene heterostructures are of great interest for use in electrocatalysis, electrochemical biosensors and graphene electrografting, making it important to understand the charge redistribution features at the metal/graphene/electrolyte interface to explain and predict their electrochemical properties. In this work, using grand-canonical DFT, the charge distribution in few-layer graphene supported on Au and Pt substrates is obtained as a function of the electrode potential and the number of graphene layers. It is shown that graphene coating on the metal surface shifts the potential of zero charge towards more negative values. A phenomenological model for describing charge distribution in the studied systems is proposed and parameterized based on DFT calculations. It can be used as a charge model for the force field intended for MD simulation of electrolytes near the electrified metal/graphene heterostructures at a fixed potential relative to the standard hydrogen electrode. The results can be used for explaining, predicting and optimizing electrochemical catalysts and biosensors based on the metal/graphene heterostructures.

The number of carbon allotropes is ever increasing with a variety of novel network topologies. Among several that were recently proposed, the K₄ structure draws particular attention due to its similarities with diamond, but it is a chiral periodic graph. However, the proposed K₄ was shown to be dynamically unstable. As a result, despite the fact that such a graph is uncommon in the allotropes of elements, the graph of K₄ is disregarded as a potential structure for elemental carbon. Herein, by means of first principles calculations, we have attempted stabilizing such a chiral graph for carbon by modulating phonon eigenvectors associated with imaginary phonon frequencies that were responsible for the structure instability. This has led us to generate six novel stable carbon allotropes, with 4- and a mix of 3,4-connected carbon atoms, that have the history of chiral K₄. The newly predicted carbon allotropes retain chirality, exhibit lower symmetry than K₄ carbon, and show improved thermodynamic stability. Among these, the thermodynamic stability increases as the ratio of 3:4 connectedness decreases. Analysis of the electronic structure suggests that the 3-connected K₄ net would prefer to be colored with elements of three valence electrons. The computed band gap suggests that all the six novel K₄ modifications predicted are semiconductors with band gaps ranging from 0.72 to 5.14 eV. In addition, the calculated elastic stiffness constants indicates that the K₄ carbon modifications are mechanically stable.

Identifying the most stable, or global-minimum (GM), structure of coordination complexes is critical across numerous scientific fields. In this work, we developed a new program called the SGMCC package, designed to search for the most stable structures of coordination complexes containing single-core or multi-cores metal centers. We introduced several improvements to the traditional genetic algorithm (GA), including the integration of isomer-specific chemical constraints, alongside the random perturbation (RP) algorithm followed by the geometry relaxation (GR) algorithm. The SGMCC package facilitates the study of micro-scale coordination structures formed by metal ions bound to ligands, with applications in areas such as seawater uranium extraction, rare earth element extraction and separation, and the separation of lanthanides/actinides and other nuclides. Additionally, the SGMCC program can accelerate the discovery of new ligands and materials for metal extraction and separation, investigate nucleation mechanisms, and analyze the dynamic structural evolution of metal complexes during nucleation. This paper presents an overview of the SGMCC package's applications.

The rotational dynamics of protonated cyanogen (NCCNH⁺) is studied for collision with both para (p-) and ortho (o-) hydrogen (H₂) in the temperature range $��1�-�100�$ K. Such cold collisions with H₂ are essential to get state-to-state rate coefficients for rotational transitions of newly detected NCCNH⁺. First, the ab initio 4D potential energy surface (PES) for NCCNH⁺-H₂ collision is generated at CCSD(T)-F12b level of theory using augmented triple zeta basis, considering rigid rotor approximation. The 4D PES is further fitted into a neural network (NN) model to augment the PES by $��\sim �130�$ folds. The PES is then expanded using bispherical harmonics functions to get radial terms, which are expressed as analytic functions. The cross-sections and rate coefficients for NCCNH⁺ are calculated using the exact close-coupling method for rotational states up to $��j�=�16�$, considering both p- and o-H₂ collisions. The rates show similar behavior to the earlier studied NCCN-H₂ collision, with the latter having larger rate coefficients.

We have combined the linear-scaling divide-and-conquer (DC) method with the semi-empirical extended tight-binding (xTB) method to develop a general-purpose large-scale quantum molecular dynamics simulation platform called DCxTBMD. Although the DC method is a fragmentation-based acceleration scheme, it is possible to perform highly accurate calculations even when adopting formal grid-based fragmentation, thanks to the mechanism called the buffer region. The program was developed by incorporating xTB Hamiltonian construction modules in the xTB program into the DCDFTBK package, a DC-based density functional tight-binding (DFTB) calculation suite. The accuracy and computational time, including the parallel scalability, of the present method were investigated on the Japanese supercomputer Fugaku, and it was found that the present method is suitable for the efficient calculation of large systems, including multiple heteroelements. We further implemented the energy gradient of the present method to enable the molecular dynamics simulation of such systems.