So entsperren Sie den Bootloader, installieren TWRP und Root Moto E5 Play


P2o5 structure

p2o5 structure Feb 01, 2016 · The Raman spectra of glasses from the compositional series (0·5–x/2)PbO. 78 P 0. Formula and structure: The chemical formula of phosphoric acid is H 3 PO 4. The distribution of [PO4]Qn species as a function of composition has been shown to slightly deviate from the . Entre las principales características del óxido de fósforo (III) se encuentran: The crystal structure of the high temperature form of niobium pentoxide. ICL Phosphate Specialties business unit primarily develops, produces, markets and sells a broad range of acids, polymeric acids and specialty phosphates for different applications in a broad range of industries. Structure of Phosphorous Pentoxide . Viscosity in the range of 10 7 and 10 11Pas was measured by a penetration method for barium phosphate and borophosphate glass melts in a series of xB2O3- (100-x)Ba (PO3)2 where x=0-12mol%. This is again due to the need to break very strong covalent bonds operating in 3-dimensions. The structure is zero-dimensional and consists of six phosphoric anhydride molecules. 232-234 . (c) a source of OH-ions in water. , thermal, optical, and luminescence properties is investigated. Data at other public NIST sites: El óxido de fósforo (III) es un compuesto cuya fórmula química es (P2O5). Structure of SnF2-SnO-P2O5 Glasses. Relevance. O. It is also used in dental cements, in the preparation of albumin derivatives, and in the sugar and textile industries. Dec 01, 2007 · structure P2O5. Oct 01, 2004 · The influence of the variation in (V 2 O 5 / P 2 O 5) ratio on the local structure of iron in V 2 O 5 –BaO–Fe 2 O 3 –P 2 O 5 glass system was investigated. IR reflectance has served as a useful complementary probe to Raman scattering on glasses. Jul 10, 2012 · The Lewis Structure, or Lewis Dot Diagram, shows the bonding between atoms of a molecule and any electrons that may exist. Molecular weight calculation: 30. The shapes of these molecules can be predicted from their Lewis structures, however, with a model developed about 30 years ago, known as the valence-shell electron-pair repulsion (VSEPR) theory. The Structure and Dynamics of Alkali Silicate [10] Abou Neel EA, Knowles JC. There are three main types of chemical formulas: empirical, molecular and structural. Phytosanitary pressure (has treated/has. The best-characterized form is the H (hexagonal) or alpha modification that consists of P4O10 molecules. K. The pure substance is unstable, disproportionating to hypochlorous acid (Cl oxidation state +1) and chloric acid (Cl oxidation state +5): Phosphoric acid, (H3PO4), the most important oxygen acid of phosphorus, used to make phosphate salts for fertilizers. W. Figure 4 shows the FCC and BCC unit cells. It is a weak acid. 350%. Showing 1-6 of 6 results for "p2o5*" . Its molecular formula is written as H 3 O 4 P and its molar mass is 97. Its metastable form is the most common form. P2o5 Bond Type 3GP Mp4 HD Video Download –. de UAA) 19. The chemical formula of this compound is P 4 O 10. Infrared analysis and Mössbauer spectroscopy were used for this propose. diphosphorus pentaoxide. EL Bouaria a Laboratory of Physico-chemical of Applied Materials, Faculty of Sciences Ben M'Sik, Hassan II University, Casablanca, Morocco Sep 09, 2021 · The article reports on the structural dependence of crystallization in Na2O-Al2O3-B2O3-P2O5-SiO2 based glasses over a broad compositional space. This compound is also known as Phosphorus Pentoxide. 6 cm-<SUP>1</SUP>) and . jnoncrysol. Hushur and S. There is no direct relationship between the formula of a compound and the shape of its molecules. Read article Similar articles. In the first P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. Martin, “Structure of Vitreous P2O5 and Alkali Phosphate Glasses,” Journal of Non-Crystalline Solids, Vol. The pyrophosphate glasses have intermediate R (~1). The Lewis diagrams can also help visualize double and triple bonds. Track and address financial and legal risks before they become reality. Dec 26, 2006 · Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P. Quelqu'un pourrait-il m'aider? Je voudrais en effet savoir comment il agit par chélation. Phosphorus pentoxide is a white solid which does not have any distinct odour. Due to this retention, high applications of P, in excess of P removal in harvested crops, push soil test levels and available P above agronomic need. Its name is Phosphoric acid, triethyl ester, polymer with oxirane and phosphorus oxide (P2O5) Silver phosphate glasses of general formula xAg2O·(100 - x)P2O5 have been investigated over compositional range from x = 40 to 62. g. 013. The changes in these glass properties are related to the glass structure modifications induced by the addn. Clients can set and manage supply chain sustainability standards – so they can measure and demonstrate progress on CSR initiatives. 2 cm-<SUP>1</SUP>, associated with the long chains of Q<SUP>2</SUP> species in Raman scattering of c-NaPO<SUB>3</SUB>. Structural evolution at short and medium range distances during crystallization of a P2O5‐Li2O‐Al2O3‐SiO2 glass - Glatz - 2020 - Journal of the American Ceramic Society - Wiley Online Library We present the in situ x-ray diffraction study of the pressure-temperature phase diagram of P2O5 and, particularly, of the liquid P2O5 structure under high pressure up to 10 GPa. That is why it is called phosphorus anhydride at times. Petr Mošner, Maryna Vorokhta, Ladislav Koudelka, Lionel Montagne, Bertrand Revel, Kristina Sklepić, Andrea Moguš-Milanković. 11. Box 1410, 50-950 Wroclaw 2, Poland A. Get PDF. Other data available: Gas phase ion energetics data. 060)O4 (☐ denotes vacancies in Ca sites). Molecular weight: 141. 184538-58-7 - NWNBIINLNDXYOX-UHFFFAOYSA-N - Phosphoric acid, triethyl ester, polymer with oxirane and phosphorus oxide (P2O5) - Similar structures search, synonyms, formulas, resource links, and other chemical information. D. Preservation of Historic Barns & Other Agricultural Buildings Abatement: Through the Agricultural Structures Preservation Easement, the preservation of historic barns and other agricultural buildings over 75 years old, is encouraged by granting property tax relief within a range of 25-75% reduction in the structure’s assessment, to owners who . The valence band, survey, and P 2s, P 2p, O 1s, and C 1s core levels are reported. These grains are resistant to weathering and become concentrated in soils and sediments downslope . of P2O5 and /or Al2O3, which were probed by FTIR, 11B MAS NMR and X- ray photoelectron spectroscopies. Glass technology , 48 (2), 78-88. Drawing steps of lewis structure of P2O5 is explained in this tutorial. P2O5, which has a molecular mass of 141. For example, FCC structures are more likely to be ductile than BCC, (body centered cubic) or HCP (hexagonal close packed). 9 g/mol. Benyounoussya ,*, L. xWO 3. Alkyl Halide Reactions. Feb 03, 2021 · Physical Properties of Diamond. 9, can usually be found as its dimeric, P4O10. 9994*5. Sep 15, 2006 · Structure of Na2O–GeO2–P2O5 glasses by X-ray and neutron diffraction. 3 Pa ( 384&#8451; ) . The base glass is composed of Q(3) and Q(4) units in the amounts predicted by stoichiometry. Jun 04, 1998 · The elastic moduli of the entire vitreous range of the system ZnO–P2O5 that can be prepared by melting ZnO and P2O5 oxides in open crucibles have been measured by ultrasonic techniques. Vigorous combustion of phosphorus in air produces a voluminous white powder which is very deliquescent and hisses when dropped into water, evolving much heat and giving a liquid of acid reaction. P2O5 CAS 1314-56-3, phosphorus pentoxide for inslulating glass Phosphorus pentoxide -- Characteristic: Easily deliquescent white crystalline powder, relevant density is 0. 109640-81-5 - Ethanol, 2-chloro-, 1,1',1''-phosphate, polymer with oxirane and phosphorus oxide (P2O5) - Similar structures search, synonyms, formulas, resource links, and other chemical information. The electron configuration of the Al 3+ ion suggests that this ion has empty 3 s , 3 p , and 3 d orbitals that can be used to hold pairs of nonbonding electrons donated by neighboring water molecules. Phosphorus P2O5 | H3O10P5 | CID 86715555 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities . It also goes by names like phosphorus anhydride and phosphorus pentoxide at times. By James York-Winegar, Tristan Harper, Carrie Brennan, Justin Oelgoetz and Andriy Kovalskiy. Three . The density of this solid is 2. The Lewis structures are useful for visualization, but do not reveal the bent structure for water (105°), the pyramidal shape for ammonia, or the tetrahedral geometry of the methane molecule. Too many Te–O bonds have distances of 0. pin. Defense Technical Information Center Phosphorus is strongly adsorbed by soil particles and readily retained in soil. Open navigation menu Unit cell structures determine some of the properties of metals. The structure of phosphate glasses strongly depends on specific structural factor namely R which represents modifier (M) to phosphor (P) ratio in the glass composition [10] [11] [12]. 82 g/cm 3 Color: white Atomic Structure : Number of Energy Levels: 3 First Energy Level: 2 Second Energy Level: 8 Structure of SnF2-SnO-P2O5 Glasses . These salient facts were observed by the early workers on phosphorus, e. Journal of Non-Crystalline Solids 2014, 390, 59-69. 013☐0. The Lewis structure of water suggests that this molecule has nonbonding pairs of valence electrons and can therefore act as a Lewis base. In the Lewis structures listed below, M and X represent various elements in the third period of the periodic table. P2O5 efficiency: 32. Bonding and - ppt download. Phosphorus pentoxide is a potent dehydrating agent as indicated by the exothermic nature of its hydrolysis: However, its utility for drying is limited somewhat by its tendency to form a protective viscous coating that inhibits further dehydration by unspent material. Compare. The functional group of alkyl halides is a carbon-halogen bond, the common halogens being fluorine, chlorine, bromine and iodine. The proton conductivities of composites were measured at room temperature under dry conditions. It shows polymorphism. (See Crystal Structure Activity) Addition of P2O5 to SiO2-Al2O3-B2O3-MgO-CaO-Na2O glass : a study of its effects on glass properties, structure and melting behaviour. Effect of the Na2O–Nb2O5–P2O5 glass additive on the structure, dielectric and energy storage performances of sodium niobate ceramics S. Materials Research Bulletin, Elsevier, 2015, 63, pp. Structure Search. Defense Technical Information Center Sep 15, 2012 · The NIST XPS Database gives access to energies of many photoelectron and Auger-electron spectral lines. the crystalline changes to amorphous vitreum, absorbing moisture when expose to the air When heating to higher . It means it is found in more than one crystalline form. 037)(Si0. by Robert Boyle in 1681. This com- In this lecture, we will be discussing the Structure of Oxides of Phosphorus - P2O5/P4O10 (Phosphorus Pentoxide)Highlight:The 5A - 15 Group Elements are Name. Dehydration of amides to nitriles [P2O5] Explained: Amides can be converted into nitriles using phosphorus pentoxide, P2O5. Unit cell structures determine some of the properties of metals. Risk Management. One observes a phonon near 1172. Local livestock breeds: 6. Dec 15, 1990 · 1. Capacity of slurry pits and manure pits: 33. Electronic structure of semiconductor oxides: InPO4, In(PO3)3, P2O5, SiO2, AlPO4, and Al(PO3)3. Presenta un aspecto de polvo o cristal blanco que reacciona violentamente con agua formando ácido fosfórico. Information on this page: Notes. Arrhenius defined an acid as: (a) a species that can donate a proton. in Er- doped borosilicate glasses on the phys. 944522 g/mol. Consequently, this functional group is polarized so that the carbon is electrophilic . Dec 20, 2019 · The present crystal structure is in accord with that of IC-(Ca 1. Warmup Write Lewis structures (dot diagrams) for the following elements: hydrogen. Bihb c,F. The significant properties of these membranes were p2o5 lewis structure. 5 mol%. The local structure around phosphorus atom has been studied via 31P nuclear magnetic resonance. Lewis structure is the distribution of the electrons around the atoms of a compound. 2. Phosphorus is strongly adsorbed by soil particles and readily retained in soil. Phys Chem Glasses 2000;11:615. Properties Of Bao-B2O3-P2O5 Glasses For Active Optical Fibres. Cite . The current investigation was focused on producing novel zinc based calcium phosphoborosilicate glasses . Mar 25, 2020 · The chemical name for P2O5 is diphosphorus pentoxide. Full text not available from this repository. 9g/cm3, sublimate at 300&#8451;, melting point is 580-585&#8451;, vapour pressure is 133. Sep 06, 2021 · SO2 Lewis Structure. 1990 Dec 15;42(17):11232-11239. . Apr 01, 2005 · The structure of this crystal is close to the behaviour of model D. The bond may result from the electrostatic force of attraction between oppositely charged ions as in . Structural characterization and physical properties of P2O5-CaO-Na2O-TiO2 glasses by Fourier transform infrared, Raman and solid-state magic angle spinning nuclear magnetic resonance spectroscopies Acta Biomater . �10. Scribd is the world's largest social reading and publishing site. Abstract Two barium niobium phosphate compounds (BaNb 2 P 2 O 11 and Ba 3 Nb 2 P 4 O 18 ) were prepared by a conventional solid-state reaction method. We meet unmet needs with a versatile line of phosphate . 39 g/cm 3. (See Crystal Structure Activity) Chlorous acid is an inorganic compound with the formula HClO 2. reports generated yearly. 11)(Si 0. Rubio-Marcose,f, A. (0·5–x/2)P 2 O 5 (x=0·1, 0·2, 0·3, 0·4, 0·5 and 0·6) were studied. Loong and S. 5 átomos de oxígeno. The central phosphorous atom is connected to an oxygen atom through a double bond and to three hydroxyl (-OH) groups through single bonds. 2:21 · P4O10 Lewis Structure Tetraphosphorus. 6,000. Created by Sal Khan. This is a strong dehydrating agent which will remove water (H2O) from amide to form nitrile . 1. Professionalism: 35. Phosphorus pentoxide. Its molecules are bonded together by weak van der Waals forces. Chlorine has oxidation state +3 in this acid. 2014. J Mater Sci Mater Med P2O5 system glasses investigated by FTIR and FT-Raman. Convert grams P2O5 to moles or moles P2O5 to grams. New refinement of the crystal structure of o-P 2 O 5 Author EL HASSAN ARBIB 1 2; ELOUADI, B 1; CHAMINADE, J. Importance of the structure on the production: 17. In this lecture, we will be discussing the Structure of Oxides of Phosphorus - P2O5/P4O10 (Phosphorus Pentoxide)Highlight:The 5A - 15 Group Elements are Name. Gatehouse and A. Crystal Structure: Monoclinic Density @ 293 K: 1. Exists in several forms but is often referred to by its empirical formula P2O5. The structure is two-dimensional and consists of two P2O5 sheets oriented in the (0, 0, 1) direction. The data described here represent the first . Homepage Categories Encyclopedia Buying Requests Suppliers Latest News Tradeshow Structure Search Home > Encyclopedia > 294-716-2 Amines, C12-14-alkyl, reaction products with hexanol, phosphorus oxide (P2O5), phosphorus sulfide (P2S5) and propylene oxide Reach Info Stoichiometry Limiting reagent, example: Soda fizz comes from sodium bicarbonate and citric acid (H 3C 6H 5O 7) reacting to make carbon dioxide, sodium citrate (Na There are three main types of chemical formulas: empirical, molecular and structural. Glasses based on the potassium tetrasilicate composition with the addition of increasing amounts of P2O5, have been prepared by the melt quench route and their structure determined by magic angle spinning NMR of Si-29, P-31 and Al-27 (impurity). O. Soil testing is the research-based method for monitoring crop-available P levels in soil and the need for P . The feature . 940P0. Wadsley. 88 Eu 2+ 0. Training activities participation: 8. P2O5 Lewis Structure Diphosphorus Pentoxide (Molecular Geometry. (b) a species that can accept a proton. The viscosity at a certain temperature increases with increasing B2O3 concentration. Kojima Institute of Materials Science, University of Tsukuba , Ibaraki 305-8573, Japan J Mater Sci Mater Med P2O5 system glasses investigated by FTIR and FT-Raman. 1016/j. 19 nm. A granular form of P 4 O 10 is used in desiccators . L. With the exception of iodine, these halogens have electronegativities significantly greater than carbon. The molar mass of phosphorus pentoxide corresponds to 283. Its P-O sigma bond length is 160 pm while its P=O bond length is 143 pm. Study free Chemistry flashcards and improve your grades. Correlation between atomic structure, structural nanoinhomogeneity, and quadratic optical nonlinearity in glasses of the K2O-TiO 2-P2O5 system Glass and Ceramics (English translation of Steklo i Keramika), 2006 We prepared four types of Eu2O3- and P2O5-doped Ca2SiO4 phosphors with different phase compositions but identical chemical composition, the chemical formula of which was (Ca1. Phosphate Specialty > Phosphate Specialty Applications > P2O5 Applications. Bonjour,j'aurais aimé savoir la formule développée du déshydratant P2O5 mais ne trouve pas sa structure sur internet. has a very high melting point (almost 4000°C). Synonyms: Phosphoric anhydride, Phosphorus . 973761*2 + 15. Click here to buy a book, photographic periodic table poster, card deck, or 3D print based on the images you see here! Mar 30, 2011 · The difference in the photocatalytic activity of the two compounds is attributed to their different electronic band structures, resulting from their different crystal-structure environments. Structure and crystallization behavior of 50CuO-xTiO2-(50-x)P2O5 - Read online for free. O-P-O bond angle is 102 ° and P-O-P bond angle . 01 ☐ 0. The fluorine breaks the PeOeP bonds and induces depolymerisation. It serves as an acidic, fruitlike flavouring in food products. doesn't conduct electricity. ROI. The database contains over 29,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines. Structure and some physical properties of the sodium ion conducting glasses inside the Na2O-Na2WO4-TiO2-P2O5 system A melt-quenched method is used to prepare homogeneous glasses inside the 20Na 2 O-(50-x)Na 2 WO 4 -xTiO 2 -30P 2 O 5 (0≤x≤25 mol%) system. However, it is named after its empirical formula, which is P 2 O 5. It usually occurs in small isolated grains, as an accessory mineral in igneous and metamorphic rocks such as granite, pegmatite, schist, and gneiss. The metaphosphate (Q3) glasses have relatively low R values (<1). 22)O 4, characterized by the tilting of [MO 4] tetrahedra , and hence it can be regarded as being made up of five types of layers (denoted by S, S’’, T, T’’, and U) that include the [MO 4] tetrahedra with different tilting directions and . [28] Stebbins JF, Farnan I, Xue XY. BibTex; Full citation . Matching game, word search puzzle, and hangman also available. 048�. Dehydration of amides to nitriles [P2O5] Dehydration of amides to nitriles [P2O5] Definition: Primary amides can be converted to nitriles with a dehydrating reagent such as P2O5. Phosphorus Pentoxide, P. It reacts powerfully with water to form ortophosphoric acid, H3PO4. Three crystalline polymorphs (H, O, O'), two distinct liquids,and several amorphous or glassy solids are recognized. Direct energy: 7. The Lewis Structure for Li is Li with one dot to the right of the element. is very hard. 9445. . May 05, 2020 · In particular, P2O5 is an efficient agent in. Two phosphorus atoms are linked through oxygen atom in lewis structure of phosphorus pentoxide (P2O5). Structure, properties, spectra, suppliers and links for: Phosphorus pentoxide, 1314-56-3, P2O5. Mu~noz d, F. One of the phosphors was composed exclusively of the incommensurate (IC) phase with superspace group Pnma(0&beta;0)00s and basic unit-cell . The structure of melt-quenched glasses has been . CAS Registry Number: 1314-56-3. M. P2O5 crystallizes in the orthorhombic Pnma space group. (d) a sourse of H + ions in water. supplier performance. Price, C. Eur J Glass Sci Technol B 2008;49:41. What is chemical bond, ionic bond, covalent bond? Chemical bond. materresbull. ence of P2O5 and Al2O3 content on the structure of erbium-doped borosilicate glasses and on their physical, thermal, optical and luminescence properties. Abstract The structure of vitreous P 2 O 5 (v-P 2 O 5 ), sodium ultraphosphate glasses, (Na 2 O) x (P 2 O 5 ) 100− x ( x =10, 20), and alkali metaphosphate glasses, MePO 3 (Me=Li, Na, K, Rb and Cs), have been studied by neutron diffraction. 41-50. Glasses from the two systems, xFe2O3 · (100-x)[P2O5 · CaO] and x(Fe2O3 · V2O5) · (100-x)[P2O5 · CaO] with 0 ≤ x ≤ 50 mol% were prepared under the same conditions and characterized by IR spectroscop. 21 nm but there is a deficit of distances of 0. A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. B. Es un anhídrido formado por: 2 átomos de fósforo. Molar mass of P2O5 = 141. Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs. P2O5 is Tungsten structured and crystallizes in the trigonal R3c space group. Monazite is a rare phosphate mineral with a chemical composition of (Ce,La,Nd,Th) (PO 4 ,SiO 4 ). �hal-01091966� We prepared four types of Eu2O3- and P2O5-doped Ca2SiO4 phosphors with different phase compositions but identical chemical composition, the chemical formula of which was (Ca1. Jan 15, 2007 · The role of the Sm 3+ ions in the structure of vitreous Sm 2 O 3 4P 2 O 5 has been investigated using the neutron diffraction anomalous dispersion technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance. During melting, P2O5 and SnF2 form a low-temperature melt, which facilitates melting of the SnO and promotes the formation of a more stable glass structure. The melting point of this P 2 O 5 is 613K. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other. Sep 22, 2003 · Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band region which shows significant differences from the phosphates. Suzuya, D. 99 g/mol. 5. 02. Predicting the Shapes of Molecules . The corresponding T(r) functions (figure 10(a)) show several differences from the T(r) of the glass tep27. P 3; DARRIET, J 3 [1] Applied Solid State Chemistry Laboratory, Faculty of Science, Charia Ibn Batota, Rabat, Morocco [2] Department of Chemistry, Faculty of Science, Kenitra, Morocco [3] Institut de Chimie de la Matière Condensée de Bordeaux, (ICMCB)-CNRS [UPR 9048], Université . We prepared four types of Eu2O3- and P2O5-doped Ca2SiO4 phosphors with different phase compositions but identical chemical composition, the chemical formula of which was (Ca1. 950Eu3+0. for Avetta clients. The bulk, s. Temporal pasture (% of land for livestock use) 18. All other oxygen atoms have made double bonds with phosphorus atom. Structural features in the neutron structure factors, S ( Q ), characteristic of intermediate-range ( Q ≲ 3 A −1 ) order were identified. Before directly jumping into the lewis structure of SO2, let’s have a quick discussion regarding the importance of lewis structure and the steps to draw it. Formula: O 5 P 2. The latest release of the Periodic Table (dated 1 Dec 2018) includes the most recent updates released in June 2018 by the IUPAC Commission on Isotopic Abundances and Atomic Weights () (see related News, released 5 June 2018), and specifically for argon, the assignment of an interval for the new standard atomic weight which reflects the common occurrence of variations in the atomic weights of . Kojima Institute of Materials Science, University of Tsukuba , Ibaraki 305-8573, Japan Mar 18, 2014 · CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses were prepared via an optimized sol–gel method. Poly(vinylidene fluoride) (PVDF) doped hybrid glass membranes were prepared with various concentrations of tetraethoxysilane (TEOS), trimethylphosphate and PVDF. DOI: 10. On the other hand, in g-NaPO<SUB>3</SUB>, the corresponding vibrational feature consists of a triad of modes; a majority mode (1165. The effect of P2O5 and /or Al2O3 addn. The significant properties of these membranes were Feb 03, 2021 · Chemsrc provides CAS#:184538-58-7 MSDS, density, melting point, boiling point, structure, etc. Energetic efficiency. Phys Rev B Condens Matter. Answer: P2O5 ( Phosphorus pentoxide ) is a covalent bond. Use this to practice the names and formulas of covalent compounds and acids. there are two inequivalent P5+ sites. p2o5 structure