PO4 Groups Research Articles

Synthesis and characterization of a novel alkali mixed magnesium-aluminum phosphate with a layered structure–KMgAl(PO4)2

A novel phosphate compound - potassium magnesium-aluminum double phosphate with chemical formula KMgAl(PO4)2 - has been synthesized. Platelet-shaped single crystals have been grown from the flux using K2Mo2O7 as a solvent. The powder form has been obtained through a sol-gel reaction. It has been characterized by X-ray diffraction, differential thermal analysis, vibrational spectroscopy and electronic structure calculations. KMgAl(PO4)2 crystallizes in the trigonal centrosymmetric space group P3¯m1 (No. 164) with unit cell parameters a = b = 5.347(1) Å, c = 7.903(10) Å, γ = 120° (Z = 1). The main characteristic of the crystal is the two-dimensional (2D) lamellar framework formed by Mg|AlO4 and PO4 tetrahedrons sharing their vertices of oxygen atoms, with the K+ cations located within the interlayer space. The sample morphology and chemical composition were revealed by the scanning electron microscopy – energy-dispersive X-ray spectroscopy analysis. The IR spectroscopy of KMgAl(PO4)2 confirmed the existence of a single PO4 group in agreement with the structural study. A relatively large indirect band gap of 3.86 eV was determined.

Contrasting effects of carbon source recalcitrance on soil phosphorus availability and communities of phosphorus solubilizing microorganisms

Carbon (C) additions to soil interact through chemical and microbiological processes to cause changes in soil phosphorus (P) availability. However, the response of soil P transformations and relevant microbial communities to C additions having different degrees of recalcitrance remains uncertain. We studied the effects of glucose, hemicellulose and lignin addition on soil P availability, P transformation processes and relevant microbial activity and communities in a P-deficient flooded soil. Lignin significantly increased soil available P concentrations, which was attributed to chemical release of inorganic P and increased alkaline phosphatase activity. Glucose and hemicellulose additions stimulated microbial metabolism of C thereby enhancing microbial demand for P, with increased soil P availability especially in the early incubation period. Glucose or hemicellulose addition changed soil microbial diversity and community composition, leading to enhanced growth and interactions of P solubilizing microorganisms such as Desulfitobacterium, Bacillus and Desulfosporosinus. Our results infer the importance of pH alteration and competitive sorption between PO4 and functional groups of recalcitrant C (e.g., lignin) with Fe/Al (hydr) oxides in regulating soil P availability. Further, the microbial response to labile C additions led to increased P availability in the P-deficient soil. This study provides important mechanistic information to guide microbially-regulated soil P management in agricultural ecosystems.

Physiochemical and bactericidal activity evaluation: Silver-augmented 3D-printed scaffolds-An in vitro study.

Injuries requiring resection of tissue followed by autogenous bone transfer may be prone to infection by Staphylococcus aureus, impeding recovery and increasing medical costs. For critical sized defects, the common approach to reconstruction is a tissue transfer procedure but is subject to limitations (e.g., donor site morbidity, cost, operating time). Utilizing beta tricalcium phosphate (β-TCP) as bone grafting material augmented with silver (Ag), a custom graft may be 3D printed to overcome limitations and minimize potential infections. Scaffolds were 3D printed and augmented with Ag by external attack on the surface by silver nitrate (AgNO3 ) at varying concentrations (0.1, 1.0, 10% wt/wt of scaffold). The augmented scaffolds were evaluated utilizing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP-MS) to verify the presence of Ag and phosphate (PO4 ) groups followed by electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to gather information of chemical and physical properties. Preliminary biocompatibility and bactericidal capacity of the scaffolds were tested using human osteoprogenitor (hOP) cells and methicillin-sensitive S. aureus strain, respectively. XRD, FTIR, ICP-MS, TGA, and DSC confirmed presence of Ag and PO4 groups, whereas electron microscopy showed a decrease in Ca and an increase in Ag ions, decreasing Ca/P ratio with increasing surfactant concentrations. PrestoBlue assays yielded an increase in fluorescence cell counts among experimental groups with lower concentrations of Ag characterized by their characteristic trapezoidal shape whereas cytotoxicity was observed at higher concentrations. Similar observations were made with alkaline phosphatase assays. Antimicrobial evaluation showed reduced colony-forming units (CFU) among all experimental groups when compared to 100% β-TCP. β-TCP scaffolds augmented with Ag ions facilitate antibacterial effects while promoting osteoblast adhesion and proliferation.

RNA Identification and Detection of Nucleic Acids as Aerosols in Air Samples by Means of Photon and Electron Interactions

This study presents a methodology to reveal traces of viral particles, as aerosol with known chemical and molecular structure, in a sample by means of photon and electron interactions. The method is based on Monte Carlo simulations and on the analysis of photon-electron fluxes-spectra through energy channels counts as a function of different aerosol viral concentrations in the air sample and looking at the peculiar photon/electron interactions with the potential abnormal atomic hydrogen (H), oxygen (O), carbon (C), and phosphorus (P) compositions present in the air sample as a function of living and nonliving matter with PO4 group RNA/DNA strands in a cluster configuration.

Towards Reversible High-Voltage Multi-Electron Reactions in Alkali-Ion Batteries Using Vanadium Phosphate Positive Electrode Materials.

Vanadium phosphate positive electrode materials attract great interest in the field of Alkali-ion (Li, Na and K-ion) batteries due to their ability to store several electrons per transition metal. These multi-electron reactions (from V2+ to V5+) combined with the high voltage of corresponding redox couples (e.g., 4.0 V vs. for V3+/V4+ in Na3V2(PO4)2F3) could allow the achievement the 1 kWh/kg milestone at the positive electrode level in Alkali-ion batteries. However, a massive divergence in the voltage reported for the V3+/V4+ and V4+/V5+ redox couples as a function of crystal structure is noticed. Moreover, vanadium phosphates that operate at high V3+/V4+ voltages are usually unable to reversibly exchange several electrons in a narrow enough voltage range. Here, through the review of redox mechanisms and structural evolutions upon electrochemical operation of selected widely studied materials, we identify the crystallographic origin of this trend: the distribution of PO4 groups around vanadium octahedra, that allows or prevents the formation of the vanadyl distortion (O…V4+=O or O…V5+=O). While the vanadyl entity massively lowers the voltage of the V3+/V4+ and V4+/V5+ couples, it considerably improves the reversibility of these redox reactions. Therefore, anionic substitutions, mainly O2− by F−, have been identified as a strategy allowing for combining the beneficial effect of the vanadyl distortion on the reversibility with the high voltage of vanadium redox couples in fluorine rich environments.

Characterization of mechanical properties and failure of potassium dihydrogen phosphate under mechanical stressing

Potassium dihydrogen phosphate (KDP) is an important material to a range of technological fields owing to its unique optical and physical properties, such as its frequency-doubling, high efficiency in nonlinear conversion and excellent photoelectric and piezoelectric capabilities. However, the basic mechanical constants of this material have never been accurately determined, and its failure mechanisms, too, have not been properly revealed. This paper aims to determine precisely the complete set of mechanical constants of KDP and investigate its failure mechanisms when the material is subjected to a variety of loading conditions. It was identified that the 6 independent mechanical constants C11, C33, C12, C13, C44 and C66 of KDP are 50.36, 50.67, −4.08, 12.58, 9.99 and 2.84 GPa, respectively; its Poisson's ratio ν is 0.24, its bulk modulus K and shear modulus G are 21.17 and 13.27 GPa, respectively; and its elastic moduli in the <100> and <001> directions, E100 and E001, are 46.14 and 43.83 GPa, respectively. It was found that the atomic structure of KDP greatly influences its anisotropy and leads to distinguished failure mechanisms in different lattice orientations. A perfect KDP crystal fails under the stress of 3.19 GPa at the strain of 10% in the <100>/<010> direction and 1.69 GPa at the strain of 5% in the <001> direction. It was also found that the deformation of KDP under a uniaxial or a biaxial strain is due to the rotation of the tetrahedron PO4 groups.

Copper phthalocyanine/fluorapatite nano composite and its pH- and photo-responsive properties

An efficient drug delivery system has been prepared using copper phthalocyanine (CuPc) and fluorapatite (CuPc-FAP). This composite showed excellent dispersibility in water compared with pure CuPc. Interestingly, unlike the CuPc, the CuPc-FAP composite exhibited strong fluorescence emission around 480 nm, which should be attributed to the restriction of intramolecular rotation of CuPc. Drug delivery experiments were carried out using glycine (Gly), histidine (His) and adenine (Aden) as the drug markers. For Gly and His, the suitable adsorption arises from electrostatic interactions between COO− groups of the drug markers and Ca+ ions of CuPc-FAP. Besides, the hydrogen bonds could be form between NH3+ of Gly and His and surface oxygen atoms of the PO4 group of CuPc-FAP. However, FTIR results showed that the CC group from the six-membered ring of Aden and the NH2 group are the suitable sites for the interaction of Aden with CuPc-FAP. The composite showed interesting properties including pH- and photo-responsive drug release, due to the co-existence of fluorapatite and CuPc, respectively. We hope that CuPc-FAP be a novel promising candidate as water dispersible drug carrier.

Daylight-White-Emitting and Abnormal Thermal Antiquenching Phosphors Based on a Layered Host SrIn2(P2O7)2.

Single-phase white-emission phosphors possess a judicious usage potential in phosphor-converted white-light-emitting diodes (WLEDs). Recently, numerous efforts have been made toward the development of new patterns of white-emitting phosphors that achieve excellent quantum yield, superior thermal stability, and applaudable cost effectiveness of WLEDs. Finding suitable single-component white phosphor hosts to provide an ideal local environment for activators remains urgent. Inspired by the original discovery of the promising host MgIn2(P2O7)2 (MIP) and its structural dependence on alkali-metal cations, we synthesized a brand-new phosphor host, SrIn2(P2O7)2 (SIP), via the traditional solid-state reaction. Its crystal structure was determined using an ab initio analysis and the Rietveld method. It belongs to a monoclinic unit cell with the space group C2/c. Besides, SIP exhibits a special layered three-dimensional framework in which the monolayer [SrO10]∞ was surrounded by a bilayer [In2P4O14]∞ made of the InO6 octahedra and P2O7 groups. A series of pure SIP:Tm3+,Dy3+ phosphors with tunable blue-white-yellow emission were prepared by adjusting the dopant concentration and utilizing the Tm3+-Dy3+ energy transfer. The daylight-white-emitting phosphor SIP:0.01Tm3+,0.04Dy3+ (the correlated color temperature is 4448 K) exhibits an abnormal thermal antiquenching property, and the emission intensity of 423 K reaches 103.7% of the initial value at 300 K. On the basis of the temperature-dependent lattice evolution and microenvironment analysis, the reduction of β and lattice distortion can lead to lower asymmetry of the activators and benefit the compensation of trapped-electron thermal activation. In this work, an integration study was carried out on the crystal structure of the new matrix, the occupation of the luminescent center, the interaction of different activators in the host, and the distortion degree of the local structure for the activators, which is of great practical sense for producing a novel single-matrix white phosphor possessing superior thermal endurance for UV-light-stimulated WLEDs.

3d‐metal (Cr to Zn) Nitrilotris(Methylenephosphonate)s with different coordination symmetries: Electronic Structure and Chemical Bond

AbstractIn this study, we present a comparative study of two parallel isostructural series of the 3d‐metal coordination complexes with nitrilotris(methylenephosphonic acid) H6{N(CH2PO3)3} (NTP, H6L) as a ligand. The series were analyzed by comparing their complexes in the spatial distribution of electron density and electron‐energy spectrum extracted from the XRD and XPS data, respectively. The first isostructural series (M=CrII, MnII, FeII, CoII, NiII, CuII, ZnII) contains a fourfold (four‐times) protonated ligand (H4L2−) and has a slightly distorted octahedral coordination of 3d‐metal atom by three O atoms of PO3 groups and three water molecules. The second isostructural series (M=MnII, CoII, CuII, ZnII) with the fully deprotonated ligand (L6−) has a distorted trigonal‐bipyramidal coordination of 3d‐metal atom with four O atoms of PO3 groups and N atom in the vertex. The complex of L6− with NiII, which is structurally close to the second series complexes, has a slightly distorted octahedral coordination of Ni atom with four O atoms of PO3 groups, N atom and an additional water molecule. For fully deprotonated PO3 groups, considerable shift of electron density is observed away from the center of the phosphorus atom to all the three P−O bonds. The protonation of only one of the oxygen atoms causes the shift of electron density from all the three P−O bonds to the center of the phosphorus atom and localization of P3s electron pair.

Carbon scaffold VPO4 as an anode for lithium- and sodium-ion batteries

In order to eliminate the short fall due to PO4 group results in an intrinsic conductivity of the material, an attempt has been made to prepare carbon-coated VPO4/C via the sol-gel method as an anode in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The as-prepared materials well wrapped with carbon, the interaction of carbon offers an efficient pathway for the conduction of carrier electrons and ions (Li+/Na+) to utilize almost the entire power of active material. This material exhibits noteworthy performances in LIBs/SIBs, by delivering an initial discharge capacity of 989/536 mAh g−1 at current density 100 mA g−1 with a capacity retention of 73/52% for the cell cycled up to 100 times.

Precision study of mineralization features of enamel apatite in the development of fluorosis by means of optical spectroscopy

We have investigated the molecular composition of the tooth enamel microregions in the normal and initial stages of the development of fluorosis by means of the IR and Raman spectroscopy. It has been shown that in the pathology of fluorosis, tooth mineralization takes place with the formation of calcium fluoroapaptite. It was found that an increased fluorine content causes a change in the characteristic profile of the bands and a redistribution of the intensity of the components of the υ1 PO4 and υ3 CO3 groups of the infrared and υ4 PO4 Raman spectra. The resulting IR and Raman spectra can be utilized as standards in the development of a new diagnostic approach of the early forms of the disease.

Color tuning of the Ba1.96Mg(PO4)2:0.04Eu2+ phosphor induced by the chemical unit co-substitution of the (BO3)3− anion group

Replacing the tricolor blend of phosphors by a single-phase white-emitting phosphor has emerged as a new technology for devising white-light-emitting diodes (WLEDs). Modification of the local structure in the crystal plays the key role in obtaining a single-phased, high CRI white-emitting phosphor. This process can also be employed to tune the color emission of the phosphor, especially those doped with Eu2+ ions. In this context, the selection of an appropriate host and the substituting chemical unit plays a vital role, as the crystal environment of the host greatly influences the photoluminescence (PL) emission of the Eu2+ ions. Herein, the color tuning of a new single-phase solid-solution Ba1.96Mg(PO4)2−x(BO3)x:0.04Eu2+ (x = 0.2, 0.5, 0.7, 1, 1.2 and 1.5) phosphor synthesized by the sol-gel/Pechini method is demonstrated. The structural variation induced by the varying composition of the borate (BO3)3− unit was analyzed by X-ray diffraction and Rietveld refinement studies. Fourier transform infrared spectroscopy revealed the presence of the vibrations corresponding to both the BO3 and PO4 chemical groups in the Ba1.96Mg(PO4)2−x(BO3)x:0.04Eu2+ phosphor. Morphological variations were also observed with the chemical co-unit substitution, which was analyzed with Scanning Electron Microscopy (SEM). PL studies indicated that the color tuning from blue-white-orange light, under near UV excitation, was achieved by varying the composition of the (BO3)3− group. The co-existence of the PO4 and BO3 groups gave rise to a higher-energy emission (420 nm) and a lower-energy emission (585 nm), respectively. The PL decay curves were analyzed to estimate the energy transfer efficiency between the higher-energy and lower-energy emission sites of the phosphor. This work presents a new strategy to tune the color emission of a singly-doped phosphor by modifying the structure of the host lattice.

Crystal Structure Refinements of Four Monazite Samples from Different Localities

This study investigates the crystal chemistry of monazite (APO4, where A = Lanthanides = Ln, as well as Y, Th, U, Ca, and Pb) based on four samples from different localities using single-crystal X-ray diffraction and electron-probe microanalysis. The crystal structure of all four samples are well refined, as indicated by their refinement statistics. Relatively large unit-cell parameters (a = 6.7640(5), b = 6.9850(4), c = 6.4500(3) Å, β = 103.584(2)°, and V = 296.22(3) Å3) are obtained for a detrital monazite-Ce from Cox’s Bazar, Bangladesh. Sm-rich monazite from Gunnison County, Colorado, USA, has smaller unit-cell parameters (a = 6.7010(4), b = 6.9080(4), c = 6.4300(4) Å, β = 103.817(3)°, and V = 289.04(3) Å3). The a, b, and c unit-cell parameters vary linearly with the unit-cell volume, V. The change in the a parameter is large (0.2 Å) and is related to the type of cations occupying the A site. The average &lt;A-O&gt; distances vary linearly with V, whereas the average &lt;P-O&gt; distances are nearly constant because the PO4 group is a rigid tetrahedron.

Polyethylene Identification in Ocean Water Samples by Means of 50 keV Energy Electron Beam

This study presents a new methodology to reveal traces of polyethylene (the most common microplastic particles, known as a structure of C2H4) in a sample of ocean water by the irradiation of a 50 keV, 1 µA electron beam. This is performed by analyzing the photon (produced by the electrons in water) fluxes and spectra (i.e., fluxes as a function of photon energy) with different types of contaminated water using an adequate device and in particular looking at the peculiar interactions of electrons/photons with the potential abnormal atomic hydrogen (H), oxygen (O), carbon (C), and phosphorus (P) compositions present in the water, as a function of living and nonliving organic organisms with PO4 group RNA/DNA strands in a cluster configuration through a volumetric cells grid.

Influence of ZnO Doping on Spectral Properties of Sol–Gel Derived CdO–FePO4 Nanocomposites

The focus of this study are the spectral properties of undoped and zinc oxide (ZnO) doped cadmium oxide iron phosphate (CdO–FePO4) nanocomposites synthesized through a sol-gel approach. Doping of ZnO into the CdO–FePO4 matrix is confirmed through various spectroscopic techniques at room temperature for 0.3 mol.%, 0.6 mol.%, and 0.9 mol.% of ZnO concentration. X-ray diffraction (XRD) pattern indicates that prepared CdO–FePO4 nanocomposites doped with ZnO correspond to the cubic crystalline nature of CdO, hexagonal amorphous nature of FePO4 and tend to form nanometer size of about 21 nm. The morphological analysis of the produced nanocomposites is done via scanning electron microscopy and transmission electron microscopy (TEM) images. The particle sizes found from TEM images are in the nanometer regime and are in good agreement with the results obtained from XRD. The functional groups corresponding to CdO bands and PO4 groups are observed for the prepared samples from Fourier transform infrared (FT-IR) and Raman spectra. The optical bandgaps of CdO–FePO4 nanocomposites doped with ZnO are deduced by diffused reflectance measurements. The photoluminescence spectrum exhibits bands in the visible range signifying the quantum confinement-induced photoluminescence, and the resultant CIE coordinates and CCT values are explored in search of their applicability in home appliances.

Physical Fundamentals of Biomaterials Surface Electrical Functionalization.

This article is focusing on electrical functionalization of biomaterial’s surface to enhance its biocompatibility. It is an overview of previously unpublished results from a series of experiments concerning the effects surface electrical functionalization can have on biological systems. Saccharomyces cerevisiae cells were used for biological experiments. The hydroxyapatite (HAp) specimens were used to investigate influence of structural point defects on the surface electrical charge. Threshold photoelectron emission spectroscopy was used to measure the electron work function of HAp and biologic samples. The density functional theory and its different approximations were used for the calculation of HAp structures with defects. It was shown that the electrical charge deposition on the semiconductor or dielectric substrate can be delivered because of production of the point defects in HAp structure. The spatial arrangements of various atoms of the HAp lattice, i.e., PO4 and OH groups, oxygen vacancies, interstitial H atoms, etc., give the instruments to deposit the electrical charge on the substrate. Immobilization of the microorganisms can be achieved on the even surface of the substrate, characterized with a couple of nanometer roughness. This cells attachment can be controlled because of the surface electrical functionalization (deposition of the electrical charge). A protein layer as a shield for the accumulated surface charge was considered, and it was shown that the protein layer having a thickness below 1 µm is not crucial to shield the electrical charge deposited on the substrate surface. Moreover, the influence of surface charge on the attachment of microorganisms, when the surface roughness is excluded, and the influence of controlled surface roughness on the attachment of microorganisms, when surface charge is constant, were also considered.

Ring-Shaped Polyoxometalate Built by {Mn 4 PW 9 } and PO 4 Units for Efficient Visible-Light-Driven Hydrogen Evolution

A novel mixed-valence, ring-shaped multinuclear Mn-containing polyoxometalate, [H2N(CH3)2]15NaH8-[MnIII3MnIV(μ3-O)3(OAc)PO4(B-α-PW9O34)]4·36H2O (1) was made and systematically characterized using v...

The Crystal-Chemical Features of Phases and the Nature of the Coordination Bond in the System [CuxNi(1 – x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1)

The structural features of the phases formed during crystallization of mixed copper and nickel complexes with nitrilotris(methylenephosphonic acid) [CuxNi(1 – x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1) and the character of the M ← O(P) coordination bond have been investigated. The copper-dominant phase [(Cu,Ni){N(CH2PO3)3}]Na4 · 13H2O (sp. gr. P $$\bar {1}$$ , Z = 2, a = 10.0096(2)–10.0118(2) A, b = 11.0311(3)–11.0330(2) A, c = 12.2893(2)–12.3038(3) A, α = 84.7180(10)°–84.785(2)°, β = 79.504(2)°–79.544(2)°, γ = 66.971(2)°–67.058(2)°) is characterized by the trigonal bipyramidal coordination of the metal atom (oxygen atoms of three different PO3 groups of the ligand molecule lie in the pyramid-base plane, and a nitrogen atom and the oxygen atom of the neighboring ligand molecule occupy opposite vertices). The nickel-containing phase [Ni(H2O){N(CH2PO3)3}]Na4 · 11H2O (sp. gr. C2/c, Z = 4, a = 11.9924(2)–12.05510(10) A, b = 18.6049(3)–18.7152(2) A, c = 21.0724(4)–21.1266(2) A, β = 104.096(2)°–104.4960(10)°) is characterized by octahedral coordination of the Ni atom (oxygen atoms of different PO3 groups of the ligand molecule are located at three meridian octahedron vertices, and a nitrogen atom, a water molecule, and the oxygen atom of the neighboring ligand molecule occupy the rest three vertices). The dependence of the interatomic distances and bond angles in the coordination sphere of the metal atom on the Cu : Ni ratio has been studied. It is shown that the transition from the trigonal bipyramidal coordination to the octahedral coordination is accompanied by a sharp increase in the ionicity of the M ← O(P) coordination bond.

Understanding Charge Storage in Hydrated Layered Solids MOPO4 (M = V, Nb) with Tunable Interlayer Chemistry.

Hydrated layered solids are interesting charge storage hosts with potentially high electrochemical activity and interlayer tunability. Although it is often possible to tune their interlayer distance by a pillaring strategy, the poor electrochemical stability of such artificial structures remains a major issue in device operation. Here we investigate the charge storage properties of MOPO4 (M = V, Nb) hydrates with a nanosheet morphology to understand the influence of the interlayer environment on cycling stability, as well as ion selectivity. While in hydrated VOPO4 interlayer H2O molecules act as compressible springs to enable fast Li-/Na-ion transport kinetics and reasonable structural reversibility, NbOPO4 layers with bridging PO4 groups serving as permanent linkers exhibit highly stable cyclability for Li-ions, owing to a zero-volume-change ion transport process. However, the latter suffers from a much larger migration energy barrier for Na-ions. Our findings not only highlight a structurally intriguing material system, but also provide insights into reviving materials with an originally unstable interlayer chemical environment, and shed light on the design principles for creating electrochemically stable charge storage hosts.

Two Pyrophosphates with Large Birefringences and Second-Harmonic Responses as Ultraviolet Nonlinear Optical Materials.

Two new pyrophosphates nonlinear optical (NLO) materials, Rb3 PbBi(P2 O7 )2 (I) and Cs3 PbBi(P2 O7 )2 (II), were successfully designed and synthesized. Both compounds exhibit large NLO effects and birefringences. Material I presents the scarce case of possessing the coexistence of large birefringence (0.031 at 1064 nm and 0.037 at 532 nm) and second harmonic generation (SHG) response (2.8× potassium dihydrogen phosphate (KDP)) in ultraviolet NLO phosphates and its SHG is the largest in the phase-matching (PM) pyrophosphates. Both I and II have three-dimensional (3D) crystal structures composed of corner-shared RbO12 (CsO11 ), RbO10 (CsO10 ), BiO6 , PbO7 (PbO6 ) and P2 O7 groups, in which P2 O7 and PbO7 (PbO6 ) units form an alveolate [PbPO]∞ skeleton frame. Theoretical calculations reveal that the P-O, Bi-O and Pb-O units are mainly responsible for the moderate birefringence and large SHG efficiency of I.