We present a comprehensive study of the band alignments two-dimensional (2D) semiconducting materials and highlight possibilities forming momentum-matched type I, II, III heterostructures, an enticing possibility being atomic heterostructures where constituent monolayers have edges at zone center, i.e., $\mathrm{\ensuremath{\Gamma}}$ valley. Our study, which includes group IV III-V compound monolayer materials, V elemental transition-metal dichalcogenides, trichalcogenides, reveals that...

The pseudolayered character of 3D bulk crystals antimony has led us to predict its 2D single-layer crystalline phase named antimonene in a buckled honeycomb structure like silicene. Sb atoms also form an asymmetric washboard black phospherene. Based on extensive analysis comprising ab initio phonon and finite-temperature molecular dynamics calculations, we show that these two phases are robust can remain stable at high temperatures. They nonmagnetic semiconductors with band gaps ranging from...

Black phosphorus is an infrared layered material. Its bandgap complements other widely studied two-dimensional materials: zero-gap graphene and visible/near-infrared gap transition metal dichalcogenides. Though highly desirable, a comprehensive characterization still lacking. Here we report systematic study of mechanically exfoliated few-layer black phosphorus, with thickness ranging from 2 to 15 layers photon energy spanning 0.25 1.36 eV. Each exhibits thickness-dependent unique spectrum...

Self-healing mechanisms of vacancy defects in graphene and silicene are studied using first-principles calculations. We investigated host adatom adsorption, diffusion, formation, revealed atomistic the healing single, double, triple vacancies single-layer silicene. Silicon adatom, which is adsorbed to at top site forms a dumbbell-like structure by pushing one Si atom underneath. The asymmetric reconstruction single induced magnetization through rebonding two dangling bonds acquiring...

We predict the stabilities of α-graphynes and their boron nitride analogues(α-BNyne), which are considered as competitors graphene two-dimensional hexagonal BN. Based on first-principles plane wave method, we investigated stability structural transformations these materials at different sizes using phonon dispersion calculations ab-initio finite temperature, molecular dynamics simulations. Depending number additional atoms in edges between corner hexagons, n, both α-graphyne(n) α-BNyne(n)...

Based on first-principles density functional calculations, we predict that nitrogen atoms can form a single-layer, buckled honeycomb structure called nitrogene, which is rigid and stable even above room temperature. This 2D crystalline phase of nitrogen, corresponds to local minimum in the Born-Oppenheimer surface, nonmagnetic insulator with saturated $\ensuremath{\pi}$ bonds. When grown substrate like Al(111) surface graphene, nitrogene binds weakly substrates hence preserves its...

The growth of the $\sqrt{3} \times \sqrt{3}$ reconstructed silicene on Ag substrate has been frequently observed in experiments while its atomic structure and formation mechanism is poorly understood. Here by first-principles calculations we show that constituted dumbbell units Si atoms arranged a honeycomb pattern. Our model shows excellent agreement with experimentally reported lattice constant STM image. We propose new for explaining spontaneous consequential structures from $3 3$...

The interaction of silicene with Si, C, H, O, Ti atoms along H$_2$, H$_2$O and O$_2$ molecules are investigated the induced functionalities thereof analyzed using first principles density functional theory. Si adatom initially adsorbed at top site pushes down atom underneath to form a dumbbell like structure 3+1 coordination. This prediction is important for research reveal new physical phenomena related formation multilayer which apparently precursor state missing layered silicon. We found...

Silica or ${\mathrm{SiO}}_{2}$, the main constituent of Earth's rocks has several 3D complex crystalline and amorphous phases, but it does not have a graphitelike layered structure in 3D. Our theoretical analysis numerical calculations from first principles predict single-layer honeycomblike allotrope, $h\ensuremath{\alpha}$ silica, which can be viewed to derived oxidation silicene intriguing atomic with reentrant bond angles hexagons. It is wide band gap semiconductor, attains remarkable...

A single graphene layer placed between two parallel Ni(111) surfaces screens the strong attractive force and results in a significant reduction of adhesion sliding friction. When layers are inserted, each is attached to one metal with binding reduces further. In motion these transition from stick-slip continuous attained, whereby nonequilibrium phonon generation through sudden processes suppressed. The corrugation strength continues decrease upon insertion third eventually saturates at...

Based on first-principles calculation we predict two new thermodynamically stable layered-phases of silicon, named as silicites, which exhibit strong directionality in the electronic and structural properties. As compared to silicon crystal, they have wider indirect band gaps but also increased absorption visible range making them more interesting for photovoltaic applications. These phases consist intriguing stacking dumbbell patterned silicene layers having trigonal structure with...

Alkali-activated materials and related alternative cementitious systems are sustainable technologies that have the potential to substantially lower CO2 emissions associated with construction industry. However, these augmented chemical compositions as compared ordinary Portland cement (OPC), which may impact evolution of hydrate phases. In particular, calcium-silicate-hydrate (C-S-H) gel, main phase in OPC, is likely be altered at atomic scale due changes bulk composition, specifically via...

Using first-principles density functional theory calculations, we showed that electronic and magnetic properties of bare Ti adatom adsorbed single-layer silicene germanene, which are charged or subjected to a perpendicular electric field, can be modified attain new functionalities. In particular, when buckled atoms have the symmetry between their planes broken, opening gap at Dirac points. The occupation 3d orbitals atom changes with charging applied inducing significant in moment. We...

Germanene, a graphene-like single-layer structure of Ge, has been shown to be stable and recently grown on Pt Au substrates. We show that Ge adatom adsorbed germanene pushes down the host atom underneath forms dumbbell structure. This exothermic process occurs spontaneously. The attractive dumbbell-dumbbell interaction favors high coverage dumbbells. Letter heralds new phases germanene, which are constructed from periodically repeating structures display diversity electronic magnetic properties.

Two-dimensional (2D) antimonene, bismuthene, and their binary compound 2D BiSb possess high spin-orbit coupling (SOC) potential topological insulator properties upon engineering structural chemical properties. Based on many-body first-principles calculations, we show that these materials can exhibit isotropic or anisotropic optoelectronic depending geometry, i.e. buckled (hb) asymmetrical washboard (aw) phases. SOC significantly alters properties, which is predominantly evident in...

Increasing cement production and its substantial contribution to anthropogenic CO2 emissions (∼5–8%) have led the pursuit of alternative, sustainable cements. These cements often contain non-negligible amounts alkalis (Na or K) which significantly influence resulting material's performance. However, precise mechanism(s) by atomic structure thermodynamic stability primary binder phase is altered remains unknown. Here, we synthesized 45 pure sodium-substituted...

Silicene and germanene derivatives constructed from periodic dumbbell units play a crucial role in multilayers of these honeycomb structures. Using first-principles calculations based on density functional theory, here we investigate the formation mechanisms energetics Group IV atoms adsorbed graphene, silicene, germanene, stanene monolayer The stabilities binding structures are further confirmed by performing ab initio molecular dynamics at elevated temperatures, except for which is subject...

In this work, authors report on the fundamental understanding of environmental stability tellurium containing 2D layers. Work reports aging mechanisms and anisotropic to isotropic transition.

The growth process of single layer graphene with and without substrate is investigated using ab initio, finite temperature molecular dynamic calculations within density functional theory. An understanding the epitaxial mechanisms in atomic level provided by exploring transient stages which occur at growing edges graphene. These are formation collapse large carbon rings together healing Stone-Wales like pentagon-heptagon defects. activation barriers for these induced defects on various...

We study the interaction of H$_2$, O$_2$, CO, H$_2$O and OH molecules with vacancy defects graphene silicene. Atoms around bare reconstruct specific chemically active sites are created. While O$_2$ CO remain intact on both pristine silicene, these can dissociate when they placed at close proximity nucleate centers for hydrogenation oxygenation. Saturation dangling bonds defect by constituent atoms dissociated gives rise to significant modification electronic magnetic properties. analyzed...

A metallic carbon monolayer in the biphenylene network (specified as C ohs) becomes an insulator upon hydrogenation CH ohs). Patterned dehydrogenation of this ohs can offer a variety intriguing functionalities. Composite structures constituted by alternating stripes and with different repeat periodicity chirality display topological properties form heterostructures tunable band-lineup or Schottky barrier height. Alternating arrangements these finite size enable one to also construct double...

We investigate a nanoscale dielectric capacitor model consisting of two-dimensional, hexagonal h-BN layers placed between two commensurate and metallic graphene using self-consistent field density functional theory. The separation equal amounts electric charge different sign in is achieved by applying perpendicular to the layers. stored charge, energy, potential difference generated are calculated from first-principles for relaxed structures. Predicted high-capacitance values exhibit...

Vertically stacked van der Waals heterostructures constitute a promising platform for providing tailored band alignment with enhanced excitonic systems. Here we report observations of neutral and charged interlayer excitons in trilayer WSe2-MoSe2-WSe2 their dynamics. The addition WSe2 layer the leads to significantly higher photoluminescence quantum yields tunable spectral resonance compared its bilayer at cryogenic temperatures. observed enhancement yield is due larger electron-hole overlap...