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The structure of precursors is used to control the formation of six possible structural isomers that contain four structural units of PbSe and four structural units of NbSe2: [(PbSe)1.14]4[NbSe2]4, [(PbSe)1.14]3[NbSe2]3[(PbSe)1.14]1[NbSe2]1, [(PbSe)1.14]3[NbSe2]2[(PbSe)1.14]1[NbSe2]2, [(PbSe)1.14]2[NbSe2]3[(PbSe)1.14]2[NbSe2]1, [(PbSe)1.14]2[NbSe2]2[(PbSe)1.14]1[NbSe2]1[(PbSe)1.14]1[NbSe2]1, [(PbSe)1.14]2[NbSe2]1[(PbSe)1.14]1[NbSe2]2[(PbSe)1.14]1[NbSe2]1. The electrical properties of these compounds vary with the nanoarchitecture. For each pair of constituents, over 20 000 new compounds, each with a specific nanoarchitecture, are possible with the number of structural units equal to 10 or less. This provides opportunities to systematically correlate structure with properties and hence optimize performance. [ABSTRACT FROM AUTHOR]

Inorganic Isomers In their Communication on page 1130 ff., D. C. Johnson et al. describe the preparation of structural inorganic isomers with NbSe2 trilayers and PbSe bilayers from designed precursors. [ABSTRACT FROM AUTHOR]

The targeted synthesis of multiple compounds with specific controlled nanostructures and identical composition is a grand challenge in materials chemistry. We report the synthesis of the new metastable compounds [(PbSe)1.00]m(MoSe2)n using precursors each designed to self-assemble into a specific compound. To form a compound with specific values for m and n, the number of atoms within each deposited elemental layer was carefully controlled to provide the correct absolute number of atoms to form complete layers of each component structural unit. On low-temperature annealing, these structures self-assemble with a specific crystallographic orientation between the component structural units with atomically abrupt interfaces. There is rotational disorder between the component structural units and between MoSe2 basal plane units within the MoSe2 layers themselves. The lead selenide constituent has a distorted rock salt structure exactly m bilayers thick leading to peaks in the off-axis diffraction pattern as a result of the finite size of and rotational disorder between the crystallites. The in-plane lattice parameters of the PbSe and MoSe2 components are independent of the value of m and n, suggesting little or no strain caused by the interface between them. These compounds are small band gap semiconductors with carrier properties dominated by defects and exhibit extremely low thermal conductivity as a result of the rotational disorder. The thermal conductivity can be tuned by varying the ratio of the number of ordered PbSe rock salt layers relative to the number of rotationally disordered MoSe2 layers. This approach, based on controlling the local composition of the precursor and low temperature to limit diffusion rates, provides a general route to the synthesis of new compounds containing alternating layers of constituents with designed nanoarchitecture. [ABSTRACT FROM AUTHOR]

Six structural isomers containing four structural units of PbSe and four structural units of NbSe2 of compositions [(PbSe)1.14]4[NbSe2]4, [(PbSe)1.14]3[NbSe2]3 [(PbSe)1.14][NbSe2]1, [(PbSe)1.14]3[NbSe2]2 [(PbSe)1.14][NbSe2]2, [(PbSe)1.14]2[NbSe2]3 [(PbSe)1.14]2[NbSe2]1, [(PbSe)1.14]2[NbSe2]2 [(PbSe)1.14] [NbSe2]1[(PbSe)1.14] [NbSe2]1, and [(PbSe)1.14]2[NbSe2] [(PbSe)1.14][NbSe2]2 [(PbSe)1.14][NbSe2] are prepared from modulated elemental precursors by annealing at 450 °C for 1 h in a nitrogen atmosphere. [ABSTRACT FROM AUTHOR]