Tw on ovel lithium nickel boride polymorphs,R T-LiNiB and HT-LiNiB,w ith layered crystal structures are reported. This family of compounds was theoretically predicted by using the adaptive genetic algorithm (AGA) and subsequently synthesized by ahydride route with LiH as the lithium source.U nique among the knownt ernary transition-metal borides,the LiNiB structures feature Li layers alternating with nearly planar [NiB] layers composed of Ni hexagonal rings with aB -B pair at the center.Acomprehensive study using ac ombination of single crystal/synchrotron powder X-ray diffraction, solid-state 7 Li and 11 BNMR spectroscopy, scanning transmission electron microscopy, quantum-chemical calculations,a nd magnetism has shed light on the intrinsic features of these polymorphic compounds.The unique layered structures of LiNiB compounds make them ultimate precursors for exfoliation studies,t hus paving aw ay toward twodimensional transition-metal borides,MBenes.

The pursuit of two-dimensional (2D) borides, MBenes, has proven to be challenging, not the least because of the lack of a suitable precursor prone to the deintercalation. Here, we studied room-temperature topochemical deintercalation of lithium from the layered polymorphs of the LiNiB compound with a considerable amount of Li stored in between [NiB] layers (33 at. % Li). Deintercalation of Li leads to novel metastable borides (Li∼0.5NiB) with unique crystal structures. Partial removal of Li is accomplished by exposing the parent phases to air, water, or dilute HCl under ambient conditions. Scanning transmission electron microscopy and solid-state 7Li and 11B NMR spectroscopy, combined with X-ray pair distribution function (PDF) analysis and DFT calculations, were utilized to elucidate the novel structures of Li∼0.5NiB and the mechanism of Li-deintercalation. We have shown that the deintercalation of Li proceeds via a “zip-lock” mechanism, leading to the condensation of single [NiB] layers into double or triple layers bound via covalent bonds, resulting in structural fragments with Li­[NiB]2 and Li­[NiB]3 compositions. The crystal structure of Li∼0.5NiB is best described as an intergrowth of the ordered single [NiB], double [NiB]2, or triple [NiB]3 layers alternating with single Li layers; this explains its structural complexity. The formation of double or triple [NiB] layers induces a change in the magnetic behavior from temperature-independent paramagnets in the parent LiNiB compounds to the spin-glassiness in the deintercalated Li∼0.5NiB counterparts. LiNiB compounds showcase the potential to access a plethora of unique materials, including 2D MBenes (NiB).

The random dynamics in H s (R n) with s ∈ (0, 1) is investigated for the fractional nonclassical diffusion equations driven by colored noise. Both existence and uniqueness of pullback random attractors are established for the equations with a wide class of nonlinear diffusion terms. In the case of additive noise, the upper semi-continuity of these attractors is proved as the correlation time of the colored noise approaches zero. The methods of uniform tail-estimate and spectral decomposition are employed to obtain the pullback asymptotic compactness of the solutions in order to overcome the non-compactness of the Sobolev embedding on an unbounded domain.