Binary metal clusters are of high interest for applications in heterogeneous catalysis and have received much attention in recent years. To gain insights into their structure and composition at the atomic scale, computer simulations can provide valuable information if reliable interatomic potentials are available. In this paper we describe the construction of a high-dimensional neural network potential (HDNNP) intended for simulations of large brass nanoparticles with thousands of atoms, which is also applicable to bulk α-brass and its surfaces. The HDNNP, which is based on reference data obtained from density-functional theory calculations, is very accurate with a root mean square error of 1.7 meV/atom for total energies and 39 meV Å −1 for the forces of structures not included in the training set. The potential has been thoroughly validated for a wide range of energetic and structural properties of bulk α-brass, its surfaces as well as clusters of different size and composition demonstrating its suitability for large-scale molecular dynamics and Monte Carlo simulations with first principles accuracy.

Spin-crossover (SCO) materials have for more than 30 years stood out for their vast application potential in memory, sensing and display devices. To reach magnetic multistability conditions, the high-spin (HS) and low-spin (LS) states have to be carefully balanced by ligand field stabilization and spin-pairing energies. Both effects could be effectively modelled by electronic structure theory, if the description would be accurate enough to describe these concurrent influences to within a few kJ/mol. Such a milestone would allow for the in silico-driven development of SCO complexes. However, so far, the ab initio simulation of such systems has been dominated by general gradient approximation density functional calculations. The latter can only provide the right answer for the wrong reasons, given that the LS states are grossly over-stabilized. In this contribution, we explore different venues for the parameterization of hybrid functionals. A fitting set is provided on the basis of explicitly correlated coupled cluster calculations, with single- and multi-dimensional fitting approaches being tested to selected classes of hybrid functionals (hybrid, range-separated, and local hybrid). Promising agreement to benchmark data is found for a rescaled PBE0 hybrid functional and a local version thereof, with a discussion of different atomic exchange factors.

The dinickel(II) dihydride complex (1 K)o fap yrazolate-based compartmental ligand with b-diketiminato (nacnac) chelate arms (L À), providing two pincer-type {N 3 }binding pockets,has been reported to readily eliminate H 2 and to serve as amasked dinickel(I) species.Discrete dinickel(I) complexes (2 Na , 2 K)ofL À are now synthesized via adirect reduction route. They feature two adjacent T-shaped metalloradicals that are antiferromagnetically coupled, giving an S = 0g round state. The two singly occupied local d x 2 Ày 2 type magnetic orbitals are oriented into the bimetallic cleft, enabling metal-metal cooperative 2e À substrate reductions as shown by the rapid reaction with H 2 or O 2 .X-ray crystallography reveals distinctly different positions of the K + in 1 K and 2 K ,s uggesting as tabilizing interaction of K + with the dihydride unit in 1 K .H 2 release from 1 K is triggered by peripheral g-C protonation at the nacnac subunits,w hich DFT calculations showl owers the barrier for reductive H 2 elimination from the bimetallic cleft.

The dinickel(II) dihydride complex (1 K)o fap yrazolate-based compartmental ligand with b-diketiminato (nacnac) chelate arms (L À), providing two pincer-type {N 3 }binding pockets,has been reported to readily eliminate H 2 and to serve as amasked dinickel(I) species.Discrete dinickel(I) complexes (2 Na , 2 K)ofL À are now synthesized via adirect reduction route. They feature two adjacent T-shaped metalloradicals that are antiferromagnetically coupled, giving an S = 0g round state. The two singly occupied local d x 2 Ày 2 type magnetic orbitals are oriented into the bimetallic cleft, enabling metal-metal cooperative 2e À substrate reductions as shown by the rapid reaction with H 2 or O 2 .X-ray crystallography reveals distinctly different positions of the K + in 1 K and 2 K ,s uggesting as tabilizing interaction of K + with the dihydride unit in 1 K .H 2 release from 1 K is triggered by peripheral g-C protonation at the nacnac subunits,w hich DFT calculations showl owers the barrier for reductive H 2 elimination from the bimetallic cleft.

Spin crossover (SCO) complexes are in the forefront of image, memory and sensing devices, with applications already established since for thirty years. In order to reach magnetic multistability conditions, the high-spin (HS) and low-spin (LS) states have to be carefully balanced by ligand field stabilization and spin pairing energies. Both of these effects could be effectively modelled by electronic structure theory, if the description would be accurate enough to describe these concurrent influences to within a few kJ/mol. Such a milestone would allow for the in silico-driven development of SCO complexes. However, so far, the ab initio simulation of such systems has been dominated by general gradient approximation density functional calculations. The latter can only provide the right answer for the wrong reasons, given that the LS states are grossly stabilized. In this contribution, we explore different venues for the parameterisation of hybrid functionals. A fitting set is provided on the basis of explicitly correlated coupled cluster calculations, with single- and multi-dimensional fitting approaches being tested to selected classes of hybrid functionals (hybrid, range separated and local hybrid). Promising agreement to benchmark data is found for a rescaled PBE0 hybrid functional and a local version thereof, with a discussion of different atomic exchange factors.