Using Hyperoptimized Tensor Networks and First-Principles Electronic Structure to Simulate the Experimental Properties of the Giant {Mn} Torus.

The single-molecule magnet {Mn} is a challenge to theory because of its high nuclearity. We directly compute two experimentally accessible observables, the field-dependent magnetization up to 75 T and the temperature-dependent heat capacity, using parameter-free theory. In particular, we use first-principles calculations to derive short- and long-range exchange interactions and compute the exact partition function of the resulting classical Potts and Ising spin models for all 84 Mn = 2 spins to obtain observables.

Long-Range Ferromagnetic Exchange Interactions Mediated by Mn-Ce-Mn Superexchange Involving Empty 4f Orbitals.

Reactions involving reductive aggregation of MnO in methanol in the presence of Ce and an excess of carboxylic acid have led to the synthesis of structurally related Ce/Mn clusters, [CeMnO(OMe)(OCBu)(MeOH)] () and [CeMnO(OCPh)(MeOH)] (), containing at least one {MnCeO} cubane unit. The cores of both clusters contain Mn units separated by three () or two () Ce ions. Fits of variable-temperature, solid-state dc and ac magnetic susceptibility data reveal dominant ferromagnetic interactions within and , resulting in the maximum = / and = 5 ground state spins, respectively, and thus suggesting significant ferromagnetic (F) interactions between the Mn units that are ≥6 Å apart and separated by four intervening bonds through diamagnetic Ce.

Theoretical prediction of magnetic exchange coupling constants from broken-symmetry coupled cluster calculations.

Exchange coupling constants (J) are fundamental to the understanding of spin spectra of magnetic systems. Here, we investigate the broken-symmetry (BS) approaches of Noodleman and Yamaguchi in conjunction with coupled cluster (CC) methods to obtain exchange couplings. J values calculated from CC in this fashion converge smoothly toward the full configuration interaction result with increasing level of CC excitation.

Three Jahn-Teller States of Matter in Spin-Crossover System Mn(taa).

Three high-spin phases recently discovered in the spin-crossover system Mn(taa) are identified through analysis by a combination of first-principles calculations and Monte Carlo simulation as a low-temperature Jahn-Teller ordered (solid) phase, an intermediate-temperature dynamically correlated (liquid) phase, and an uncorrelated (gas) phase. In particular, the Jahn-Teller liquid phase arises from competition between mixing with low-spin impurities, which drive the disorder, and intermolecular strain interactions. The latter are a key factor in both the spin-crossover phase transition and the magnetoelectric coupling.

Exploring the Magnetic Properties of the Largest Single-Molecule Magnets.

The giant {Mn} and {Mn} wheels are the largest nuclearity single-molecule magnets synthesized to date, and understanding their magnetic properties poses a challenge to theory. Starting from first-principles calculations, we explore the magnetic properties and excitations in these wheels using effective spin Hamiltonians. We find that the unusual geometry of the superexchange pathways leads to weakly coupled {Mn} subunits carrying an effective = 2 spin.

A gate defined quantum dot on the two-dimensional transition metal dichalcogenide semiconductor WSe2.

Two-dimensional layered materials, such as transition metal dichalcogenides (TMDCs), are promising materials for future electronics owing to their unique electronic properties. With the presence of a band gap, atomically thin gate defined quantum dots (QDs) can be achieved on TMDCs. Herein, standard semiconductor fabrication techniques are used to demonstrate quantum confined structures on WSe2 with tunnel barriers defined by electric fields, therefore eliminating the edge states induced by etching steps, which commonly appear in gapless graphene QDs.