This study aims to examine the equilibrium Kesterite structure of Cu2BeSnS4, Cu2BeSnSe4, and Cu2BeSnTe4 by the application of density functional theory (DFT) and the Full-Potential Linearized ...Augmented Plane Wave (FP-LAPW) method. The study demonstrates that both Cu2BeSnS4 and Cu2BeSnSe4 compounds are semiconductors with direct band gaps at the Γ point, while Cu2BeSnTe4 has an indirect band gap (Γ→X). The electronic and optical characteristics of these materials indicate their potential utility in optoelectronic, photonic, and photovoltaic applications. Furthermore, a thorough comparison has been conducted between the obtained results and other experimental and theoretical data from the same chalcogenide family. In summary, the findings offer valuable information on the possible photovoltaic uses of these compounds.
We present the results of first-principle calculations using the Vienna Ab initio Simulation Package (VASP) for a class of organometallics labeled TM3C6O6 (TM = Sc, Ti, V, Cr, Fe, Co, Ni, and Cu) in ...the form of planar, two-dimensional, periodic freestanding layers. These materials, which can be produced by on-surface coordination on metallic surfaces, have a kagome lattice of TM ions. Calculating the structural properties, we show that all considered materials have local magnetic moments in the ground state, but four of them (with Fe, Co, Ni, and Cu) show spin-crossover behavior or switch between magnetic and nonmagnetic states by changing the lattice constant, which could be valuable for possible epitaxy routes on various substrates. Surprisingly, we find a very large richness of electronic and magnetic properties, qualifying these materials as highly promising metal-organic topological quantum materials. We find semiconductors with nearestneighbor ferromagnetic (FM) or antiferromagnetic (AFM) couplings for V, and Sc, Ti, and Cr, respectively, being of potential interest to study spin ice or spin liquids on the 2D kagome lattice. Other TM ion systems combine AFM couplings with metallic behavior (Fe and Ni) or are ferromagnetic kagome metals like Cu3C6O6 with band crossings at the Fermi surface. For the latter compound, the spin-orbit coupling is shown to be responsible for small gaps which makes them a candidate material to observe the quantum anomalous Hall effect.
We report on the successful on-surface synthesis of metal-organic covalent coordination networks with a dense Kagome lattice of metallic centers. In the case of Mn centers ab-initio calculations show ...that the adsorbed monolayer on Ag(111) has all the characteristic features of a strictly two-dimensional (2D) ferromagnetic Kagome metal. Tetrahydroxyquinone (THQ) and metal atoms (M=Cu or Mn) are co-deposited on the Ag(111) substrate to build well-ordered 2D lattices M\(_3\)C\(_6\)O\(_6\). The surface is studied by scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) to optimize the growth conditions like fluxes and temperatures. The details of the atomic, electronic and magnetic structures are clarified by density functional theory (DFT) calculations. XPS and DFT reveal a Cu\(^+\) charge state and no local magnetic moments for the Cu-organic network. For the Mn-organic network, we find the charge state Mn\(^{2+}\) and a local spin S=5/2. Charge transfer stabilizes the Cu\(^+\) and Mn\(^{2+}\) charge states. We find two different modifications of the M\(_3\)C\(_6\)O\(_6\) lattice. DFT calculations which neglect the small spin-orbit coupling show a Dirac point, i.e. a band crossing with linear electron dispersion at the K-point of the Brillouin zone. This Dirac point is at the Fermi level if there is no charge transfer but drops by 100 meV if electron doping of Cu\(_3\)C\(_6\)O\(_6\) on Ag(111) surface is acknowledged. We predict the magnetic couplings of an isolated M\(_3\)C\(_6\)O\(_6\) monolayer to be short range and antiferromagnetic leading to high frustration at the Kagome lattice and a tendency towards a spin-liquid ground state. In the case of hole transfer from the substrates ferromagnetic ordering is introduced, making M\(_3\)C\(_6\)O\(_6\) an interesting candidate for the quantum anomalous Hall effect.
The \(GW\) approximation is a well-established method for calculating ionization potentials and electron affinities in solids and molecules. For numerous years, obtaining self-consistent \(GW\) total ...energies in solids has been a challenging objective that is not accomplished yet. However, it was shown recently that the linearized \(GW\) density matrix permits a reliable prediction of the self-consistent \(GW\) total energy for molecules F. Bruneval et. al. J. Chem. Theory Comput. 17, 2126 (2021) for which self-consistent \(GW\) energies are available. Here we implement, test, and benchmark the linearized \(GW\) density matrix for several solids. We focus on the total energy, lattice constant, and bulk modulus obtained from the \(GW\) density matrix and compare our findings to more traditional results obtained within the random phase approximation (RPA). We conclude on the improved stability of the total energy obtained from the linearized \(GW\) density matrix with respect to the mean-field starting point. We bring compelling clues that the RPA and the \(GW\) density matrix total energies are certainly close to the self-consistent \(GW\) total energy in solids if we use hybrid functionals with enriched exchange as a starting point.
The $GW$ approximation is a well-established method for calculating
ionization potentials and electron affinities in solids and molecules. For
numerous years, obtaining self-consistent $GW$ total ...energies in solids has
been a challenging objective that is not accomplished yet. However, it was
shown recently that the linearized $GW$ density matrix permits a reliable
prediction of the self-consistent $GW$ total energy for molecules F. Bruneval
et. al. J. Chem. Theory Comput. 17, 2126 (2021) for which self-consistent $GW$
energies are available. Here we implement, test, and benchmark the linearized
$GW$ density matrix for several solids. We focus on the total energy, lattice
constant, and bulk modulus obtained from the $GW$ density matrix and compare
our findings to more traditional results obtained within the random phase
approximation (RPA). We conclude on the improved stability of the total energy
obtained from the linearized $GW$ density matrix with respect to the mean-field
starting point. We bring compelling clues that the RPA and the $GW$ density
matrix total energies are certainly close to the self-consistent $GW$ total
energy in solids if we use hybrid functionals with enriched exchange as a
starting point.
