Phosphorus Dimer Research Articles

Theoretical study on the spectroscopic and transition properties of phosphorus dimer cation

The potential energy curves of 18 Λ-S states of the P2 + cation have been constructed using the internally contracted multi-reference configuration interaction approach combined with the Davidson correction. The basis-set extrapolation to the complete basis set limit is performed. The relativistic effect is considered in calculations. Treatment of scalar relativistic effect at the third-order Dkroll-Hess approximate and spin-orbit coupling with the state-average Breit-Pauli operator is made. Based on the obtained potential energy curves, the spectroscopic parameters for all bound Λ-S and Ω states are determined. These results are in agreement with experiment where the spectroscopic data are available. The transition dipole moments are calculated. The properties of the dipole-allowed transitions among doublet or quartet Λ-S states are evaluated, from which Einstein coefficients, Franck-Condon factors and radiative lifetimes are estimated. The spin-orbit coupling effect on the transition properties of the 12Πg→X2Πu system is also studied. The spectroscopic and transition properties reported in this study can be used to guide the detection of phosphorus dimer cation in spectroscopy experiments.

Prediction of thermal properties of phosphorus dimer – The analytical approach

In this study, modified hyperbolical-type oscillator was used to simulate the internal vibration of a diatomic molecule. By employing the expression of partition function of the system, new analytical equations for the prediction of molar entropy, enthalpy, Gibbs free energy, and isobaric specific heat capacity were derived. The thermodynamic equations were applied to ground-state phosphorus dimer. Average absolute deviations of 0.3795, 0.8939, 0.3895, and 0.6978% were obtained. The results are in good agreement with existing data on gaseous phosphorus molecules in the literature.

Gibbs free energy of gaseous phosphorus dimer

We establish an analytical representation for the prediction of the molar Gibbs free energies of gaseous diatomic molecule substances. By comparing the predicted values to the experimental data for the gaseous phosphorus dimer, the availability of the Gibbs free energy calculation model is verified. The present model is related to three molecular constants and away from the need of lots of experimental spectroscopy data.

Entropy of gaseous phosphorus dimer

Based on the improved Rosen-Morse oscillator for describing the internal vibration of a molecule, we establish an explicit representation of molar entropy for gaseous substances. Using the dissociation energy, equilibrium internuclear distance and harmonic vibrational frequency, we calculate the molar entropy values of the gaseous phosphorus dimer. Our calculated results show an excellent agreement compared to the experimental data in a wide variety of temperatures ranging from 298 up to 6000 K.

Enthalpy of gaseous phosphorus dimer

We present an explicit representation of molar enthalpy for gaseous substances based on the improved Rosen-Morse oscillator to describe the internal vibration of a molecule. We calculate molar enthalpy values of gaseous phosphorus dimer in terms of experimental values of three molecular constants, and obtain excellent agreement between the calculated values and experimental data in a temperature range of 298–6000 K.

One-Pot Chlorine-Free Synthesis of Chiral Organophosphorus Compounds from Elemental Phosphorus and α-Methylstyrene Dimer

Direct phosphorylation of α-methylstyrene dimer with red phosphorus in KOH/DMSO superbasic system has provided the preparation of 4-methyl-2,4-diphenylpentylphosphonous acid (heating at 105°C for 3 h) or tris(4-methyl-2,4-diphenylpentyl)phosphine oxide (microwave irradiation, 15 min) in 21 and 38% yield, respectively.

Two-Dimensional Phosphorus Porous Polymorphs with Tunable Band Gaps.

Exploring stable two-dimensional (2D) crystalline structures of phosphorus with tunable properties is of considerable importance partly due to the novel anisotropic behavior in phosphorene and potential applications in high-performance devices. Here, 21 new 2D phosphorus allotropes with porous structure are reported based on topological modeling method and first-principles calculations. We establish that stable 2D phosphorus crystals can be obtained by topologically assembling selected phosphorus monomer, dimer, trimer, tetramer, and hexamer. Nine of reported structures are predicted to be more stable than white phosphorus. Their dynamic and thermal stabilities are confirmed by the calculated vibration spectra and Born-Oppenheimer molecular dynamic simulation at temperatures up to 1500 K. These phosphorus porous polymorphs have isotropic mechanic properties that are significantly softer than phosphorene. The electronic band structures calculated with the HSE06 method indicate that new structures are semiconductors with band gaps ranging widely from 0.15 to 3.42 eV, which are tuned by the basic units assembled in the network. Of particular importance is that the position of both conduction and valence band edges of some allotropes matches well with the chemical reaction potential of H2/H(+) and O2/H2O, which can be used as element photocatalysts for visible-light-driven water splitting.

Study on sublimation of solid electrolyte (AgI)0.5‐(AgPO3)0.5with Knudsen effusion mass spectrometry

Knudsen high-temperature mass spectrometry was used to study the process of sublimation of a solid electrolyte (AgI)(0.5-)(AgPO(3))(0.5). Monoatomic iodine ions were found to be the dominant species in the electron ionization mass spectra below 600 degrees C. With an increase in temperature, the relative content of phosphorus oxide ions, mainly [PO](+) and [P(4)O(10)](+), increased. Under further heating, we observed silver iodide and iodine dimer ions together with phosphorus dimer and tetramer ions and clusters [IPO(2)](+), [IP(2)](+), [I(3)P](+). Using the experimental logarithmic dependencies of ion signal intensities versus the reciprocal absolute temperature of the effusion cell, the apparent sublimation enthalpies Delta(s)H of the ions giving the most intense signals were estimated.

In-Rich Surface Growth on P-Rich InP(001) (2 × 1) Surface: Structural and Mechanistic Study

Metal−organic chemical vapor deposition (MOCVD) is a widely used method for the growth of compound semiconductor surfaces using gas-phase precursors. In this work, we have used density functional calculations and cluster models to investigate the growth of the In-rich indium phosphide surface resulting from the chemical reaction of InH3 with the P-rich (2 × 1) surface. In particular, the thermodynamics and kinetics of the individual steps involved in the growth are considered thoroughly. The highest barrier corresponds to the initial reaction involving InH3 dissociation on the phosphorus dimer. The detailed mechanisms as well as the energetics of the different steps are discussed.

Indium phosphide (001)-(2×1): Direct evidence for a hydrogen-stabilized surface reconstruction

The surface structure of the indium phosphide $(001)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ reconstruction has been clarified in this work. Infrared spectra collected during atomic deuterium titration of the InP $(001)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ surface reveal a sharp P-H stretching mode at 2308 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Based on theoretical cluster calculations using density-functional theory, this mode results from a single hydrogen atom bonded to one end of a buckled phosphorus dimer. These results confirm that the $(2\ifmmode\times\else\texttimes\fi{}1)$ structure is hydrogen stabilized as recently proposed in the literature.

Structure-sensitive oxidation of the indium phosphide (001) surface

The oxidation of anion- and cation-rich indium phosphide (001) has been investigated by exposure to unexcited molecular oxygen. Indium phosphide oxidation is an activated process and strongly structure sensitive. The In-rich δ(2×4) surface reacts with oxygen at 300 K and above. Core level x-ray photoemission spectra have revealed that the O2 dissociatively chemisorbs onto the δ(2×4), inserting into the In–In dimer and In–P back bonds. By contrast, the P-rich (2×1) reconstruction does not absorb oxygen up to 5×105 Langmuir at 300 K, as judged by the unperturbed reflectance difference spectrum and low energy electron diffraction pattern. Above 455 K, oxygen reacts with the (2×1) inserting preferentially into the In–P back bonds and to a lesser extent into the phosphorus dimer bonds.

Filled- and empty-state imaging of (2×4) reconstructed InP(001) surfaces with STM

InP(001) surfaces prepared by sputter-annealing and by annealing in a P 2 atmosphere have been studied using scanning tunnelling microscopy (STM). Annealing a phosphorus-rich (2×1) surface to above 600 K leads to the formation of the (2×4) surface. The filled- and empty-state STM images obtained from large areas with ordered (2×4) reconstruction are consistent with a two phosphorus dimer–two missing dimer model. The transition from (2×1) to (2×4) reconstruction proceeds through an intermediate stage where local regions showing mixed (2×4)/(2×2) forms are observed.

Evaluation of plasma and thermal sources for atomic hydrogen-assisted epitaxy of InP

Homoepitaxial layers of InP have been grown on (100) InP substrates by gas source molecular beam epitaxy while simultaneously exposed to an atomic hydrogen flux produced either by plasma or by thermal cracking. The thermal H-assisted growths were performed with various H fluxes, H2 cracker cell temperatures, PH3 cracker cell temperatures, annealing conditions, and Be doping levels. Photoluminescence and Hall effect studies indicate improved optical and electrical properties of the InP layers grown in the presence of H as compared to layers grown by conventional epitaxy without H. This improvement is attributed to a reduction in point defects due to the removal of unwanted phosphine cracker products, such as P4, from the sample surface during growth by reaction with H. The reconstructed 2×1 H-terminated surface may also reduce P vacancy defects due to the absence of the missing phosphorus dimer row present on the conventional 2×4 surface. Problems associated with donor impurity contamination, which increased with thermal source temperature, were avoided by use of the plasma source.

Surface photoabsorption study of the effects of growth temperature and V/III ratio on ordering in GaInP

Surface photoabsorption (SPA) measurements were used to clarify the Cu–Pt ordering mechanism in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. The Cu–Pt ordering is strongly affected by the growth temperature and the input partial pressure of the phosphorus precursor, i.e., the V/III ratio. SPA was used to measure the concentration of [1̄10]-oriented phosphorus dimers on the surface, which are characteristics of the (2×4) reconstruction, as a function of the growth temperature and V/III ratio. The degree of order decreases markedly with increasing growth temperature above 620 °C at a constant V/III ratio of 40 [tertiarybutylphosphine (TBP) partial pressure of 50 Pa]. This corresponds directly to a decrease of the P-dimer concentration on the surface. Below 620 °C, the degree of order decreases as the growth temperature decreases, even though the concentration of P dimers increases. This is most likely due to the slow migration of adatoms on the surface during growth. The degree of order is found to decrease monotonically with decreasing V/III ratio in the range from 160 to 8 at 670 °C. This corresponds directly to the decrease of the P-dimer concentration on the surface. The direct correlation of the [1̄10]-oriented phosphorus dimer concentration and the degree of order with changes in both temperature (≥620 °C) and V/III ratio suggests that the (2×4) surface reconstruction is necessary to form the Cu–Pt structure, in agreement with published theoretical studies. The physical structure of the surface of these Ga0.5In0.5P layers was also characterized, using atomic force microscopy. For growth at 670 °C and a V/III ratio of 160, the structure of the layers growth on exactly (001) oriented GaAs substrates consists of islands surrounded mainly by bilayer (approximately 6 Å) steps. As the V/III ratio is reduced, the step height transforms to one monolayer. Exclusively monolayer steps are formed at a V/III ratio of 8. This is interpreted in terms of the stabilization of the bilayers by formation of the (2×2) reconstruction on the (111)B step face at high V/III ratios.

A mass spectrometry study of the gas pyrolysis of PH 3 and a PH 3/Si 2H 6 mixture

The thermal dissociation of phosphine and of a phosphine—disilane gas mixture as a function of temperature has been studied in an impinging jet type LPCVD reactor. In order to measure the influence of homogeneous gas phase reactions, two configurations (cold and hot wall) were used. A quadrupole mass spectrometer (QMS) coupled with the reactor using a sampling system near the substrate surface was used to follow the gas phase composition. PH 3 begins to decompose at 550°C. Formation of the phosphorus dimer (P 2) and tetramer (P 4) is demonstrated; P 4 is the main product. When Si 2H 6 is added to this gaseous mixture, formation of monosilylphosphine SiPH 5 is observed.

Effects of core correlation on atomic and dimeric phosphorus

The effects of core correlation on the bond distance and binding energy for the phosphorus dimer are investigated, and it is shown that these effects are substantial; the bond distance is reduced by almost 0.02 Å and the D e increased by 0.2 eV through core correlation. Two strategies are used to calculate the core-correlation contributions: explicit correlation of the (2s, 2p) core orbitals and use of the core polarization potential (CPP) method. In order to determine the CPP parameters, calculations of ionization potentials and some excitation energies for atomic phosphorus are also performed. Most of the calculations are done at the MR-ACPF level of correlation, using a CASSCF reference function, but also the CCSD, CCSD (T) and the recently developed CASPT2 methods are used. Different basis sets, ranging from an uncontracted (21s16p10d5f2g) basis to a [5s4p3d2f] ANO contracted basis, are used to investigate basis set effects. Our calculated values for the bond distance and the dissociation energy are 1.893 Å and 4.92 eV, respectively, which are in good agreement with the experimental results ( r e=1.893 Å, D e=5.08 eV).

A PH3 cracking furnace for molecular beam epitaxy

A furnace was fabricated to crack phosphine in ultrahigh vacuum. Thermodynamic calculations showed that phosphine should dissociate into the phosphorus dimer to a high degree. Furnace materials were compared by construction of all-tantalum and all-quartz cartridges which slid into the furnace hot zone. Phosphine was found to react with tantalum, but not to any great extent with quartz. The effects of baffles, studied with the quartz cartridges, lowered the temperature at which the cracking efficiencies began to increase and increased cracking efficiencies. The temperature range studied was from 100 ° to 1170 °C.