Structural evolution, magnetic moment, and thermochemical and spectral properties of NdSi
n
0/−
(
n
= 8–20) nanoclusters were studied. Optimized structures for NdSi
n
demonstrated that the ...configuration with quintet ground state prefers Nd-substituted for a Si of the most stable Si
n
+ 1
(
n
= 8–11) structure to Nd-linked configuration with Si
9
tricapped trigonal prism subcluster (
n
= 12–19). Finally, the configuration prefers to Nd-encapsulated into Si cage framework (
n
= 20). For anion, the evolution at the quartet state prefers Nd-linked structure for
n
= 8–19 (excluded 9), and prefers Nd-encapsulated structure of
n
= 20. The spectral information including electron affinity, vertical detachment energy, and simulated photoelectron spectroscopy were also observed. The 4
f
electrons of Nd atom in NdSi
n
with
n
= 8–10 hardly participate in bonding, but take part in remaining neutral clusters and all anionic NdSi
n
−
clusters. The calculations of average bond energy, HOMO-LUMO gap, and chemical bonding analyses reveal that NdSi
20
−
possesses perfect thermodynamic and ideal chemical stability, making it as the most appropriate constitutional units for novel multi-functional semiconductors.
Graphical abstract
The equilibrium structures and electronic properties such as relative stabilities, electron affinities, and charge transfer of small neutral and charged FeSi
n
(−1,0,+1)
(
n
= 1–6) clusters have ...been systematically studied using the high level of the correlation consistent Composite Approach (ccCA) method. The lowest-energy geometries of these clusters can be regarded as “substitutional structure.” It is derived from Si
n + 1
(and/or Si
−
n + 1
) clusters by replacing a silicon atom with an iron atom. The adiabatic electron affinities (AEAs) and the adiabatic ionization potentials (AIPs) have also been predicted by ccCA schemes for FeSi
n
(
n
= 1–6) and their ions. The dissociation energies of an iron or a silicon atom from the ground-state structure of FeSi
n
clusters have been evaluated to check relative stabilities of FeSi
n
(−1,0,+1)
(
n
= 1–6) clusters. Compared with other clusters, neutral and charged FeSi
2
possess higher stability. As for the neutral clusters and the negatively charged ions, the theoretical charges of the iron atom in FeSi
n
(
n
= 1–6) species (except for FeSi and FeSi
2
−
) show that silicon clusters act as an electron donor. For the cationic species, however, the charge transfers from iron atom to silicon clusters (except for FeSi
3
+
) show that the iron atom acts as electron donor.
We have carried out a global search of systematic isomers for the lowest energy of neutral and Zintl anionic Zr-doped Si clusters ZrSin0/-/2- (n = 6–16) by employing the ABCluster global search ...method combined with the mPW2PLYP double-hybrid density functional. In terms of the evaluated energies, adiabatic electron affinities, vertical detachment energies, and agreement between simulated and experimental photoelectron spectroscopy, the true global minimal structures are confirmed. The results reveal that structural evolution patterns for neutral ZrSin clusters prefer the attaching type (n = 6–9) to the half-cage motif (n = 10–13), and finally to a Zr-encapsulated configuration with a Zr atom centered in a Si cage (n = 14–16). For Zintl mono- and di-anionic ZrSin-/2-, their growth patterns adopt the attaching configuration (n = 6–11) to encapsulated shape (n = 12–16). The further analyses of stability and chemical bonding make it known that two extra electrons not only perfect the structure of ZrSi15 but also improve its chemical and thermodynamic stability, making it the most suitable building block for novel multi-functional nanomaterials.
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•Ultrasonic synthesis was used to create a range of sulfur-functionalized metal–organic frameworks (S-MOFs: Bi-TDC) that exhibit piezo photocatalytic properties.•Rapid reduction of ...hexavalent chromium (Cr(VI) using piezo photocatalysis.•A method and reduction mechanism for reducing hexavalent chromium (Cr(VI)) is proposed.
The United Nations’ Sustainable Development Goals (SDGs) are significant in guiding modern scientific research. In recent years, scholars have paid much attention to MOFs materials as green materials. However, piezo catalysis of MOFs materials has not been widely studied. Piezoelectric materials can convert mechanical energy into electrical energy, while MOFs are effective photocatalysts for removing pollutants. Therefore, it is crucial to design MOFs with piezoelectric properties and photosensitivity. In this study, sulfur-functionalized metal–organic frameworks (S-MOFs) were prepared using organic sulfur-functionalized ligand (H2TDC) ultrasonic synthesis to enhance their piezoelectric properties and visible light absorption. The study demonstrated that the S-MOFs significantly enhanced the reduction of a 10 mg/L solution of hexavalent chromium to 99.4 % within 10 min, using only 15 mg of catalyst. The orbital energy level differences of the elements were analyzed using piezo response force microscopy (PFM) and X-ray photoelectron spectroscopy (XPS). The results showed that MOFs functionalized with sulfur atom ligands have a built-in electric field that facilitates charge separation and migration. This study presents a new approach to enhance the piezoelectric properties of MOFs, which broadens their potential applications in piezo catalysis and piezo-photocatalysis. Additionally, it provides a sustainable method for reducing hexavalent chromium, contributing to the achievement of sustainable development goals, specifically SDG-6, SDG-7, SDG-9, and SDG-12.
A systematic investigation
of the silver-doped germanium clusters
AgGe
n
with
n
= 1–13
in the neutral, anionic, and cationic states is performed using the
unbiased global search technique combined ...with a double-density functional
scheme. The lowest-energy minima of the clusters are identified based
on calculated energies and measured photoelectron spectra (PES). Total
atomization energies and thermochemical properties such as electron
affinity (EA), ionization potential (IP), binding energy, hardness,
and highest occupied molecular orbital-lowest unoccupied molecular
orbital (HOMO-LUMO) gap are obtained and compared with those of pure
germanium clusters. For neutral and anionic clusters, although the
most stable structures are inconsistent when
n
=
7–10, their structure patterns have an exohedral structure
except for
n
= 12, which is a highly symmetrical
endohedral configuration. For the cationic state, the most stable
structures are attaching structures (in which an Ag atom is adsorbed
on the Ge
n
cluster or a Ge atom is adsorbed
on the AgGe
n
–1
cluster) at
n
= 1–12, and when
n
= 13, the cage
configuration is formed. The analyses of binding energy indicate that
doping of an Ag atom into the neutral and charged Ge
n
clusters decreases their stability. The theoretical EAs
of AgGe
n
clusters agree with the experimental
values. The IP of neutral Ge
n
clusters
is decreasing when doped with an Ag atom. The chemical activity of
AgGe
n
is analyzed through HOMO-LUMO gaps
and hardness, and the variant trend of both versus cluster size is
slightly different. The accuracy of the theoretical analyses in this
paper is demonstrated successfully by the agreement between simulated
and experimental results such as PES, IP, EA, and binding energy.
By performing density functional theory (DFT) calculations for geometric optimization in conjunction with the artificial bee colony algorithm for cluster (ABCluster) global search approach, the ...ground-state structures of the neutral, anionic, and dianionic ZrSnn0/-/2- (n = 4-17) nanoscale compounds are obtained. Their structural growth evolution, spectral information, and electronic and thermochemical properties are investigated. Regarding the architectural evolution of the neutral, anion, and dianionic species, ZrSnn0/-/2- (n = 4-17) compounds possess two different stages of adsorption patterns in which, when n = 4-7 and n = 8-17, ZrSn40/-/2- and ZrSn80/-/2- compounds as the basic motif adsorb Sn atoms to become the larger clusters, respectively. The simulated photoelectron spectra (PES) of anionic compounds are in good agreement with the available experimental PES. The infrared and Raman spectra can be summarized as follows: under infrared vibrational modes, the sealed cages of ZrSnn0/-/2- compounds belong to the deformation mode, and under Raman vibrational modes, they belong to the breathing mode of the Sn cage framework. The density of states (DOS) spectra and natural population analysis (NPA) indicate that the interaction between the Zr atom and Snn frameworks of capsulated compounds has been developing stronger than for unsealed compounds. The results of thermochemical properties, molecular orbital shell (MOs) analysis, and ultraviolet-visible (UV-vis) absorption spectrum indicate that the neutral ZrSn16 nanoscale compound possesses not only both thermodynamic and chemical stability but also far-infrared sensing and optoelectronic properties and hence, is the best building block motif for new multipurpose nanoscale materials.
Equilibrium geometries, thermodynamic stabilities, chemical reactivities, and electronic properties of neutral, mono-, and di-anionic Hf-doped silicon nanoclusters HfSi
n
0/−2-
(
n
= 6–16) are ...calculated by employing an ABCluster global search technique combined with mPW2PLYP scheme. Based on the concordance between simulated and experimental PES, the true global minima are confirmed for
n
= 6, 9, and 12–16. Optimized geometries for neutral HfSi
n
nanoclusters can be divided into three stages: first, Hf atom prefers locating on the surface site of the cluster for
n
= 6–9, which can be obtained by adding one, two, three, and four Si atoms to HfSi
5
tetragonal bipyramid, respectively (denoted as additive type); then, Hf atom is surrounded by Si atoms with half-cage configuration for
n
= 10–13; finally, Hf atom is encapsulated into Si cage pattern for
n
= 14–16. For mono-anions, it is from additive type (
n
= 6–11) to the cagelike configuration with Hf atom resided in silicon clusters (
n
= 12–16). For di-anions, it is additive type (
n
= 6–9) to the Hf-linked configuration (
n
= 10–11), and in the end to the Hf-encapsulated cagelike motif (
n
= 12–16). The thorough analysis of stability and chemical bonding revealed that the neutral HfSi
16
and di-anionic HfSi
15
2−
are magic nanoclusters with good thermodynamic and chemical stability, which may make them as the most suitable building block for new functional materials. We suggest that the experimental PES of HfSi
n
−
with
n
= 7, 8, 10, and 11 should be further examined due to the lack of comparably low electron binding energy peaks.
The rare earth dope d nano-cluster can be a building block for the next-generation photo-electrical industry, so the imminent discovery of novel, suitable nano-functional material is urgent. ...Praseodymium element as a wonderful dopant, bestow a novel photoelectrochemical properties for nanomaterials especially for semiconductor, derived from its unfulfilled 4f electrons configuration and active electronic transitions between 4f to 4f and 4f to 5d. In view of this, the neutral and anionic clusters of PrSin0/- with a medium size of n = 10–20 are comprehensively investigated by the quantum chemistry method of mPW2PLYP associated with the global searching potential energy surface techniques. The geometry evolution in medium size for PrSin can be attributed to three stages of replaced (n = 10–12), linked (n = 13–19), and cage (n = 20) structure. For PrSin-, two evolution phases are obviously observed by linked (n = 10–19) and cage (n = 20) structure. The PES spectra of the anionic most stable cluster and several degeneracy structures are simulated to identify the ground state structure. Each cluster of AEA, charge transfer, and VDE values are all calculated. Combined with binding energy, HOMO-LUMO gap, molecular orbital analysis, and a series of optical properties estimated, including simulated UV–vis, IR, and Raman spectra, excitation behavior shows PrSi20- has not only prominent stability but also has a proper range of lighting absorption, higher electron-hole recombination, possible as a functional material for optoelectronic devices.
•Nano-clusters PrSin0/- (n = 10–20) studied by double hybrid density functional theory.•Praseodymium doped in silicon clusters can improve the stabilities and make new unique photoelectric characteristics.•Structure evolution, photoelectron spectroscopy, HOMO-LUMO gap.•As excellent building blocks, potentially applied to multifunctional optical and electrical nanomaterials.
To know the details of the habitat selection and home range of black-necked cranes (Grus nigricollis) and how grazing influences them, we observed juvenile members of the population with satellite ...tracking in the Danghe wetland of the Yanchiwan National Nature Reserve in Gansu from 2018 to 2020 during the months of July–August. Population monitoring was also conducted during the same period. The home range was quantified with kernel density estimation methods. Then, we utilized remote sensing image interpretation with machine learning to identify different habitat types in the Danghe wetland. Manly’s selection ratios and random forest model were employed to assess habitat selection in home range scale and habitat scale. In the study area, a grazing restriction policy was implemented in 2019, and the response of Black-necked cranes suggest as follows: a) the number of young cranes increased from 23 to 50, which indicates a grazing regime affects cranes fitness; b) the current grazing regime does not affect the areas of home range and the selection of habitat types, but it affects the crane’s use of space as the mean overlap index of the home range was 1.39% ± 3.47% and 0.98% ± 4.15% in 2018 and 2020 years, respectively; c) there was an overall increasing trend in mean daily movement distance and instantaneous velocity indicate a movement ability increases of young cranes, and the ratio of disturbed cranes becomes greater; d) Human disturbance factors have little effect on habitat selection, and cranes are hardly affected by houses and roads currently. The cranes selected lakes, but comparing the home range and habitat scale selection, marsh, river and mountain range cannot be ignored. Therefore, we believe that continuing the grazing restriction policy will help to reduce the overlap of home ranges and subsequently reduce intraspecific competition, and then it increases the safety of movements of young cranes, and ultimately increases population fitness. Further, it is important to manage the water resources and maintain the existing distribution of roads and buildings throughout the wetlands.
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