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While most existing theoretical studies on the borophene are based on first-principles calculations, the present work presents molecular dynamics simulations for the lattice dynamical and mechanical properties in borophene. The obtained mechanical quantities are in good agreement with previous first-principles calculations. The key ingredients for these molecular dynamics simulations are the two efficient empirical potentials developed in the present work for the interaction of borophene with low-energy triangular structure. The first one is the valence force field model, which is developed with the assistance of the phonon dispersion of borophene. The valence force field model is a linear potential, so it is rather efficient for the calculation of linear quantities in borophene. The second one is the Stillinger-Weber potential, whose parameters are derived based on the valence force field model. The Stillinger-Weber potential is applicable in molecular dynamics simulations of nonlinear physical or mechanical quantities in borophene.

Microscopic phonon theory of semiconductor nanocrystals (NCs) is reviewed in this paper. Phonon modes of Si and Ge NCs with various sizes of up to 7 nm are investigated by valence force field theory. Phonon modes in spherical SiGe alloy NCs approximately 3.6 nm (containing 1147 atoms) in size have been investigated as a function of the Si concentration. Phonon density-of-states, quantum confinement effects, as well as Raman intensities are discussed.

In an approximation of the generalized valence force field, the frequencies and forms of the normal vibrations of the free molecule of spiroanthraceneoxazine (SAO) are calculated. The vibrational spectra of SAO are measured: the IR absorption spectra in an NaCl disk and the Raman spectra in a KBr disk. The calculated and experimental data were correlated with the aid of a method of refined initial data. The results obtained agree with the calculated and experimental spectra of model and related compounds.

In the approximation for the valence force field with quantum-chemical estimation of the intensities of the absorption bands of IR spectra, calculation of the main spectral-structural and energy characteristics of dioxy-benzenes is performed. This made it possible to suggest energetically more favorable conformations and assign the frequencies of normal vibrations to individual types of symmetry.

In this paper, room temperature PL spectra of InAs self-assembled dots grown on GaAs/InP and InP substrate are presented. For analyzing different positions of the PL peaks, we examine the strain tensor in these quantum dots (QDs) using a valence force field model, and use a five-band k·p formalism to find the electronic spectra. We find that the GaAs tensile-stained layer affects the position of room temperature PL peak. The redshift of PL peak of InAs/GaAs/InP QDs compared to that of InAs/InP QDs is explained theoretically.

The vibrational spectra of adenine and its deuterium-substituted analogs are calculated in the valence force field approximation. The frequencies and forms of normal vibrations of the molecule at 1700–300 cm-1 are interpreted.

The structure of the NbOCl3 molecule is studied by electron diffraction at 743(6) K. It is established that the molecule is characterized by C3v symmetry and the following structural parameters: rα(Nb=0) 1.682(6) A, rα(Nb−Cl) 2.276(5) A, ∢(ONbCl) 107.5(5)°, and ∢(ClNbCl) 111.3(4)°. Comparison with the other niobium oxytrihalide molecules shows that these values of the Nb=O bond and the bond angles are characteristic. The assignment of the ϕ3 frequency of the NbOCl3 molecule is refined, and the vibration frequencies of the NbOF3 molecule are estimated.

The local structures of Si1−xGex solid solutions can be described with FDUC model (the five distorted unit cells) based on a phenomenological valence force field approach. Bond lengths and strain energies in these solid solutions can be predicted. The distorted feature of the local structure is well described by the five distorted unit cells. Calculated results are compared with those obtained from EXAFS, indicating the excellent agreement between theoretical predictions and EXAFS measurements with the largest divergence not larger than 0.01 A. In addition, The relationship betweenSi1−xGex and III–V random solid solutions is also discussed.

Quick, facile, and high-yield syntheses of di- and trinegative octachloro- and octabromoditechnetates by reduction of tetrahalogenooxotechnetates(V) or hexahalogenotechnetates(IV) with tetrahydridoborate in organic solvents are described. The compounds are easily convertible by ligand exchange reactions. Under exclusion of air the octahaloditechnetates(lII, III) are stable in organic solvents and unstable in conc. hydrohalic acids, in contrast to the octahaloditechnetates(II, III) being stable in conc. hydrohalic acids and unstable in organic solvents. Based on a general valence force field, normal coordinate analyses on the metal-metal multiple bond systems [Re2X8]2− (X = F, Cl, Br, I), [Tc2X8]2−,3− (X = Cl, Br)(D4h), including35Cl and37Cl labeled species, and [Os2X8]2− (X = Cl, Br, I)(D4d) have been performed. With sets of seven or ten force constants very good agreement between observed and calculated frequencies has been achieved. The metal-metal valence force constants range from 2.7 to 4.9 mdyne/A, the strength of the bonds depending on the bond order and the masses of the ligands. The bromo compounds in particular exhibit a strong vibrational coupling of the metal-metal stretching mode with the symmetric breathing vibration of the ligand sphere.

InxGa1-xN alloys are investigated by combining density-functional theory (DFT) calculations and all extended valence force field model (VFF). Based on a large nuniber of ordered InxGa1-xN supercells we determined the accuracy of various valence force field models with respect to ab initio DFT calculations. To get the correct energy difference between the stable wurtzite and the inetastable zincblende phase the inclusion of the ion-ion-interaction within the VFF’ model was necessary. As a direct consequence the inequivalent bonds of the wurtzite structure including the non-ideal c/a ratio and internal u parameter are described correctly. The wurtzite phase is found to be stable against the zincblende phase for all concentrations. The calculated elastic constants and their dependency on In alloy composition enables the determination of the local concentration by simultaneous measurement of the local lattice constants a and c.

We have studied the growth of lattice mismatched semiconductors through the association of the Monte Carlo technique and the Valence Force Field (VFF) approximation. The Monte Carlo technique monitors the atomic motion in the deposited layer using the Arrhenius law and taking into account the impingment of atoms from the gas phase, intralayer and interlayer migrations of atoms and evaporation from the surface. The VFF approximation is used as an energy model to determine the local strain and stress inside the deposited layer by minimizing the total energy. This is performed after each single atomic motion. The strain is assumed to enhance the atomic motion by lowering the activation energy barrier related to the particular event. Results concerning the case of large lattice mismatches are presented. It is observed that the growing surface becomes rapidly rough, showing grooves with (111) facets. The strain relaxation occurs as a result of this roughening and allows the determination of the critical thickness. At higher lattice mismatches, it is seen that the layer orientation changes from(100) to (111) from the beginning.

We study the elastic strain relaxation in highly strained layers deposited on a [001] substrate induced by coherent 3D islanding. We first calculate the elastic strain distribution within several pyramidal 3D islands with different faces (the observed ones being usually [114] or [014]). For this, we use a valence force field (VFF) description. Our calculation includes interactions between islands, which appear to be a key parameter. We study how the shape of the island modifies the strain relaxation which is proved to vary within the island. Very simple considerations on surface tension indicate why pyramidal islands are the most stable.

Within a valence force field framework, we calculate the critical thickness of a film lattice mismatched to the substrate on which it is epitaxially deposited. A capping layer lattice matched to the substrate is known to enhance the critical thickness. We calculate the efficiency of the capping layer and study how the capping layer thickness modifies this efficiency. We also demonstrate how using a capping layer which is no more lattice matched to the substrate may improve the effect of the capping layer. Extension to strain compensation in multilayer systems is provided. In the case of uncapped systems, or systems with a thick capping layer lattice matched to the substrate, the results we have obtained using a microscopic description are compared to recent results, obtained using continuous classical elasticity.

The rotational spectra of ONF in the (100), (010) and (001) excited vibrational states were observed and the corresponding vibrationratation α constants determined. A centrifugal-distortion analysis of 156 ground-state rotational transitions yielded accurate values of all the sextic centrifugal-distortion constants. Both vibration-rotation α constants and sextic centrifugal-distortion constants were used to determine, by least-squares methods, the cubic part of the general valence force field of nitrosyl fluoride. Anab initio calculation provided reliable constraints for the three cubic terms of the potential-energy function which are not directly determinable by the available experimental data.

The polarised Raman spectra of the three isomeric trifluoromethyl benzonitriles have been recorded in the region 50–4000cm−1. The near and farir spectra of these compounds have been recorded in the region 200–4000 cm−1 and 33–700 cm−1 respectively. To check the vibrational assignments normal coordinate analysis was performed using general valence force field. Very good agreement has been achieved between the observed and the calculated fundamental frequencies. It has been possible to resolve the controversies about the assignments of the C-CF3 stretching and CF3 symmetric stretching modes in substituted trifluoromethyl benzenes. Vibrational assignments together with the force fields for three isomers are reported for the first time.

A complete vibrational analysis of the methyl ammonium ion CH3NH3+, and of CD3NH3+, CH3ND3+ and CD3ND3+ is described in this paper. A General valence Force Field has been computed for these ions, belonging to C3ν sysmmetry, using the fundamental frequencies obtained from the infrared spectra. The mean square amplitudes and shrinkage constants and Coriolis coupling constants have also been calculated for the first time and presented here.

The infrared absorption spectrum ofγ-phenylpyridine has been recorded experimentally in the range 600–2000 cm−1 and the fundamental frequencies and forms of the normal vibrations have been calculated using the valence force field. The experimental and calculated data show satisfactory agreement.

A normal co-ordinate analysis of ethylene oxide, ethylene oxide-d4 and ethylene sulphide is carried out and the potential energy constants are determined using both the most general quadratic potential function and Urey-Bradley force field. Using the potential energy constants obtained by the former method the mean amplitudes of vibration of these molecules are calculated by the secular equation method. The thermodynamic properties of these molecules are reported for the ideal gaseous state at one atmosphere pressure for eleven temperatures from 100° K. to 1000° K.

Using the proper geometry of methanol, a 16-parameter valence force field has been calculated for CH3OH, CD3OH, CH3OD and CD3OD.

General Valence force constants have been evaluated for GeH3CCH and GeD3CCH. Generalised mean-square amplitudes of vibration have been obtained and the shrinkage constants have been calculated using the perpendicular mean-square amplitudes of vibration. Coriolis coupling constants have also been determined.

Urey-Bradley force field (UBFF) and orbital valence force field (OVFF) techniques have been applied to the hexachloride and the hexabromide anions (O h symmetry) of tantalum(I) and niobium(I). Trends in stretching force constants have been discussed on the basis of (i) the periodic position of the central metal atom and (ii) the nature of the halide ligands. Comments have been made also on the suitability of the force fields used.