Electron spectra of Me7Eu2UO2(PO4)5 crystals

Absorption and luminescence spectra of Me₇Eu₂UO₂(PO₄)₅ crystals (Me represents Na, Rb, or Cs) are investigated. It is established that the luminescence of Eu³⁺ ions in these crystals is sensitized by uranyl. The effect of the outer-sphere cation Me⁺ on the spectroscopic properties and structural features of the compounds under study is considered. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 89–94, January–February, 1999.     

Study on lattice vibrational properties and Raman spectra of Bi_2Te_3 based on density-functional perturbation theory

We present a variational density-functional perturbation theory(DFPT) to investigate the lattice dynamics and vibrational properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states(DOS) of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field,atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO–TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.     

Raman spectroscopic study of the uranyl phosphate mineral dumontite Pb2 [(UO2)3O2(PO4)2]·5H2 O

Raman spectra of dumontite were measured at 298 and 77 K. Observed bands were attributed to the stretching and bending vibrations of uranyl and phosphate units and OH stretching vibrations of water molecules. U–O bond lengths in uranyls and approximate O–H···O bond lengths were calculated. The values of the U–O bond lengths are in agreement with the data from the single crystal structure analysis of dumontite. Copyright © 2008 John Wiley & Sons, Ltd.     

An algebraic approach to the comparative study of the vibrational spectra of monofluoroacetylene (HCCF) and deuterated acetylene (HCCD)

Using the Lie algebraic method the vibrational energy levels of HCCF and HCCD are calculated for 102 and 110 vibrational bands, respectively, using the local Hamiltonian. A comparative study is made between the two. Better results are obtained than those published earlier from local mode analysis.     

Vibrational spectra and structural dynamic models of halosubstituted formaldehyde

The DFT/B3LYP method with 6-31G*(**) basis sets has been used to analyze the vibrational spectra of halo-substituted formaldehyde in the anharmonic approximation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 683–686, September–October, 2006.     

Density functional theory calculations and vibrational spectra of p‐bromonitrobenzene

FT‐IR and FT‐Raman spectra of p‐bromonitrobenzene (p‐BNB) have been recorded in the region 4000–400 cm⁻¹ and 4000–50 cm⁻¹, respectively. The molecular structure, geometry optimization, vibrational wavenumbers have been investigated. The spectra were interpreted with the aid of normal coordinate analysis based on the density functional theory (DFT) using the standard B3LYP/6‐31G method and basis set combination and was scaled using multiple scale factors yielding good agreement between observed and calculated wavenumbers. The results of the calculations are applied to simulate infrared and Raman spectra of the title compound which showed reasonable agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of the vibrational spectra of (CH3)3GeCl from experimental and DFT calculations

New infrared (for gas and liquid phase) and Raman (for liquid) spectra were measured for the chlorotrimethylgermane to obtain a complete assignment of its fundamental modes. The measurement of the low‐temperature infrared spectrum together with the application of Fourier self‐deconvolution to the Raman spectra resolves the C H vibrational modes into their components. The Rauhut and Pulay scaled quantum mechanical (SQM) force field methodology and the wavenumber‐linear scaling (WLS) method were used to predict the vibrational spectra as a guide to the assignment of the fundamental bands. A quantum mechanical analysis was carried out to obtain the harmonic force field. Copyright © 2009 John Wiley & Sons, Ltd.     

First-principles study of the structural, elastic, electronic, optical, and vibrational properties of intermetallic Pd2Ga

The structural,elastic,electronic,optical,and vibrational properties of the orthorhombic Pd2Ga compound are investigated using the norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory.The calculated lattice parameters have been compared with the experimental values and found to be in good agreement with these results.The second-order elastic constants and the other relevant quantities,such as the Young’s modulus,shear modulus,Poisson’s ratio,anisotropy factor,sound velocity,and Debye temperature,have been calculated.It is shown that this compound is mechanically stable after analysing the calculated elastic constants.Furthermore,the real and imaginary parts of the dielectric function and the optical constants,such as the optical dielectric constant and the effective number of electrons per unit cell,are calculated and presented.The phonon dispersion curves are derived using the direct method.The present results demonstrate that this compound is dynamically stable.     

The luminescence properties of Eu2+ doped Na2CaMg(PO4)2 phosphor

The blue-emitting phosphors of Eu²⁺-doped Na₂CaMg(PO₄)₂ were prepared by high-temperature solid-state reaction. The crystal phase formation was confirmed by X-ray powder diffraction measurement. The luminescence properties were investigated by photoluminescence excitation and emission spectra. The phosphor exhibited the blue luminescence due to the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ions under the excitation of near UV light. The influence of temperature on the luminescence intensities and decay lifetimes of Eu²⁺ was investigated. An unusual increase of the decay lifetimes of the 4f⁶5d emission of Eu²⁺ ion is observed in Na₂CaMg(PO₄)₂ from 10 K to room temperature. The thermal stability of the luminescence of Eu²⁺-doped Na₂CaMg(PO₄)₂ was discussed.     

Experimental study of the vibrational spectra of (CH3)3GeBr supported by DFT calculations

The infrared and Raman spectra of bromotrimethylgermane (BTMG) were recorded afresh to complete the assignment of its vibrational spectra. The vibrational spectrum of BTMG has been predicted from hybrid density functional theory calculations (B3LYP) with several basis sets. The resulting harmonic wavenumbers were scaled by Pulay's scaled quantum mechanical (SQM) and the wavenumber‐linear scaling (WLS) methods to obtain accurate force fields which could aid in the vibrational assignment. Low‐temperature infrared techniques together with Fourier self‐deconvolution (FSD) on the Raman spectrum were used to improve the resolution of the spectra for the modes that could not be observed before. An SQM analysis was carried out to obtain the valence force constants and a set of scale factors that best reproduced the experimental data. Copyright © 2008 John Wiley & Sons, Ltd.     

Se_7环两种构型的结构和红外振动光谱的理论研究

在从头算层次上采用自洽场Hartree -Fock(SCF -HF)与密度泛函理论 (DFT)的定域自旋密度泛函SVWN和杂化泛函B3LYP方法以及 6 - 31 G(d)基组 ,计算优化了Se7环chair和boat两种分子构型。以B3LYP/ 6 - 31 G(d)优化的结构为基础 ,计算了Se7环两种构型的红外振动光谱 ,标定了这两种构型的各个简谐振动模式的对称性。计算结果与前人的理论、实验数据进行了比较。     

Vibrational spectra of the layered monofluorophosphate (V), NH4Ag3(PO3F)2

The powder Fourier‐transform (FT) infrared (IR) and Raman spectra of the recently characterized NH₄Ag₃(PO₃F)₂ were recorded and are discussed with a site‐symmetry analysis based on its known structural data. Some comparisons are made with the solution spectra of the PO₃F²⁻ anion and with those of crystalline Ag₂PO₃F. Copyright © 2009 John Wiley & Sons, Ltd.     

钨酸钇钠晶体中Tm3+的光谱特性

测量了Tm3 :NaY(WO4 ) 2 晶体的吸收光谱、发射光谱和激发光谱 ,利用J_O理论计算了钨酸钇钠晶体的强度参数 :Ω2 =7 2 130 4× 10 - 2 0 cm2 ,Ω4 =0 5 0 4 76 6× 10 - 2 0 cm2 ,Ω6 =0 977784× 10 - 2 0 cm2 ,以及Tm3 的光学参数包括各能级的荧光寿命和荧光分支比、积分发射截面等 ,在计算了Tm3 的自发辐射概率时 ,同时考虑了电偶极跃迁和磁偶极跃迁 .研究了其发光特性和跃迁通道 ,发现存在1 D2 3H6 →1 G4 3F4 的交叉弛豫     

Raman spectroscopic study of the uranyl mineral natrouranospinite (Na2,Ca)[(UO2)(AsO4)]2· 5H2O

Raman spectra of natrouranospinite complemented with infrared spectra were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental and theoretical investigation of vibrational spectra of copper phthalocyanine: polarized single‐crystal Raman spectra,isotope effect and DFT calculations

The IR‐ and Raman spectra of copper phthalocyanine (CuPc), as well as the isotopic wavenumber shifts upon ¹⁵N substitution in CuPc, were investigated experimentally and theoretically. The symmetry of molecular vibrations was determined using polarized Raman spectra of an oriented CuPc single crystal. Density functional theory (DFT) calculations were used for the detailed assignment of different bands in the vibrational spectra of CuPc. Theoretically predicted geometry, wavenumbers and isotopic shifts are in a very good agreement with the experimental values. A comparison of experimentally obtained isotopic shifts with theoretical predictions allowed us to reveal some characteristic features of normal vibrations of CuPc molecule. Copyright © 2009 John Wiley & Sons, Ltd.