Theoretical Calculations of Mechanical, Electronic, and Chemical Bonding in CaN2, SrN2, and BaN2

2014 ◽  
Vol 69 (12) ◽  
pp. 619-628 ◽  
Author(s):  
Li-Qin Zhang ◽  
Yan Cheng ◽  
Zhen-Wei Niu ◽  
Chang-Ge Piao ◽  
Guang-Fu Ji
Keyword(s):  
Bulk Modulus ◽  
Bond Length ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Applied Pressure ◽  
Theoretical Data ◽  
High Hardness ◽  
Mechanical Instability ◽  
Spin Polarized ◽  
The Impact

AbstractWe present a first-principles density functional theory-based study about the impact of pressure on the structural and elastic properties of bulk CaN2, SrN2, and BaN2. Non-spin and spin polarized calculations indicate that the non-spin polarized ground state was more favourable with magnetic moments of 1.049 μB, 1.059 μB, and 1.014 μB for CaN2, SrN2, and BaN2, respectively, and these were in good agreement with previous experimental and theoretical data. The high bulk modulus of CaN2, SrN2, and BaN2 confirm that those compounds have low compressibility and high hardness. The obtained bulk modulus, N-N bond length, and optimized structure parameters are similar to those from previous studies.With an increase in applied pressure the independent elastic constants of CaN2, SrN2, and BaN2 indicated the presence of mechanical instability at 20, 15, and 10 GPa, which is possibly related to phase transitions in addition to a decrease in N-N bond length.

scholarly journals Accuracy and Reliability in the Simulation of Vibrational Spectra: A Comprehensive Benchmark of Energies and Intensities Issuing From Generalized Vibrational Perturbation Theory to Second Order (GVPT2)

2021 ◽  
Vol 8 ◽  
Author(s):  
Qin Yang ◽  
Marco Mendolicchio ◽  
Vincenzo Barone ◽  
Julien Bloino
Keyword(s):  
Perturbation Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Computational Cost ◽  
Theoretical Data ◽  
Infrared Region ◽  
Second Order ◽  
Basis Set ◽  
Molecular Systems ◽  
The Impact

Vibrational spectroscopy represents an active frontier for the identification and characterization of molecular species in the context of astrochemistry and astrobiology. As new missions will provide more data over broader ranges and at higher resolution, especially in the infrared region, which could be complemented with new spectrometers in the future, support from laboratory experiments and theory is crucial. In particular, computational spectroscopy is playing an increasing role in deepening our understanding of the origin and nature of the observed bands in extreme conditions characterizing the interstellar medium or some planetary atmospheres, not easily reproducible on Earth. In this connection, the best compromise between reliability, feasibility and ease of interpretation is still a matter of concern due to the interplay of several factors in determining the final spectral outcome, with larger molecular systems and non-covalent complexes further exacerbating the dichotomy between accuracy and computational cost. In this context, second-order vibrational perturbation theory (VPT2) together with density functional theory (DFT) has become particularly appealing. The well-known problem of the reliability of exchange-correlation functionals, coupled with the treatment of resonances in VPT2, represents a challenge for the determination of standardized or “black-box” protocols, despite successful examples in the literature. With the aim of getting a clear picture of the achievable accuracy and reliability of DFT-based VPT2 calculations, a multi-step study will be carried out here. Beyond the definition of the functional, the impact of the basis set and the influence of the resonance treatment in VPT2 will be analyzed. For a better understanding of the computational aspects and the results, a short summary of vibrational perturbation theory and the overall treatment of resonances for both energies and intensities will be given. The first part of the benchmark will focus on small molecules, for which very accurate experimental and theoretical data are available, to investigate electronic structure calculation methods. Beyond the reliability of energies, widely used for such systems, the issue of intensities will also be investigated in detail. The best performing electronic structure methods will then be used to treat larger molecular systems, with more complex topologies and resonance patterns.

Structural and Vibrational Properties of Manganese Sulfide

2013 ◽  
Vol 209 ◽  
pp. 186-189
Author(s):  
Brijmohan Y. Thakore ◽  
A.Y. Vahora ◽  
S.G. Khambholja ◽  
A.R. Jani
Keyword(s):  
Bulk Modulus ◽  
Density Functional ◽  
Local Density ◽  
Theoretical Calculations ◽  
Manganese Sulfide ◽  
High Symmetry ◽  
Isothermal Bulk Modulus ◽  
Pressure Derivative ◽  
Density Functional Perturbation Theory ◽  
Quantum Espresso

Structural properties of MnS have been studied using plane wave pseudopotential density functional theory as implemented in Quantum Espresso code. Local density approximation (LDA) along with ultrasoft pseudopotential has been used for total energy calculations. The calculated total energies are fitted to Murnaghan equation of state to calculate equilibrium lattice constant, isothermal bulk modulus and pressure derivative of isothermal bulk modulus for NaCl-type structure of MnS and compared with previous experimental and theoretical calculations and good agreement is achieved with those results. Phonon frequencies have also been derived for B1 phase of MnS along high symmetry directions using the density functional perturbation theory at ambient condition.

Investigation of the structural, electronic, elastic and thermodynamic properties of Curium Monopnictides: An ab initio study

2017 ◽  
Vol 31 (30) ◽  
pp. 1750226 ◽  
Author(s):  
H. Baaziz ◽  
Dj. Guendouz ◽  
Z. Charifi ◽  
S. Akbudak ◽  
G. Uğur ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Structural Phase ◽  
Full Potential ◽  
Generalized Gradient ◽  
Metallic Behavior ◽  
Spin Polarized

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 [Formula: see text]B. The mechanical properties of CmX (X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C[Formula: see text] and C[Formula: see text], the entropy [Formula: see text] and the Grüneisen parameter [Formula: see text] have been foreseen at expanded pressure and temperature ranges.

The structures, phase transition and elastic and thermodynamic properties of ZnS from first-principles calculations

2021 ◽  
pp. 2150143
Author(s):  
Bo Li ◽  
Weiyi Ren
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Theoretical Data ◽  
Debye Model ◽  
Volume Curve ◽  
Temperature And Pressure

The phase transition of zinc sulfide (ZnS) from Zinc-blende (ZB) to a rocksalt (RS) structure and the elastic, thermodynamic properties of the two structures under high temperature and pressure are investigated by first-principles study based on the pseudo-potential plane-wave density functional theory (DFT) combined with the quasi-harmonic Debye model. The lattice constant [Formula: see text], bulk modulus [Formula: see text] and the pressure derivative of bulk modulus [Formula: see text]’ of the two structures are calculated. The results are in good agreement with experimental results and the other theoretical data. From the energy–volume curve, enthalpy equal principle and mechanical stability criterion, the transition pressures from the ZB to the RS structure are 16.83, 16.96 and 16.61 GPa, respectively. The three results and the experimental values 14.7–18.1, 16 GPa are very close to each other. Then the elastic properties are also calculated under the pressure ranging from 0 to 30 GPa. Finally, through the quasi-harmonic Debye model, the thermodynamic properties dependence of temperature and pressure in the ranges between 0–1600 K and 0–30 GPa are obtained successfully.

BULK MODULUS CALCULATIONS FOR GROUP-IV CARBIDES AND GROUP-III NITRIDES

2004 ◽  
Vol 18 (24) ◽  
pp. 1247-1254 ◽  
Author(s):  
A. MAHMOOD ◽  
L. E. SANSORES ◽  
J. HEIRAS
Keyword(s):  
Bulk Modulus ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Wide Band ◽  
Group Iii Nitrides ◽  
Group Iv ◽  
Hard Coatings ◽  
Generalized Gradient ◽  
Group Iii ◽  
Quantum Mechanical Method

Wide band gap semiconductors such as group-IV carbides ( SiC , GeC ) and group-III nitrides ( AlN , GaN and BN ) are known to be important materials for novel semiconductor applications. They also have interesting mechanical properties such as having a particularly high value for their bulk modulus and are therefore potential candidates for hard coatings. In this paper we report the theoretical calculations for the bulk modulus for zincblende and wurzite polytypes of these materials. The Density Functional and Total-energy Pseudopotential Techniques in the Generalized Gradient approximation, an ab initio quantum mechanical method, is used to obtain the theoretical structure, from which equilibrium lattice parameters and volume of the cell versus pressure may be extracted. The Murnaghan's equation of state is then used to calculate bulk modulus under elastic deformation, which is related to the hardness of a material under certain conditions. The results for bulk modulus are compared with other theoretical and experimental values reported in the literature.

scholarly journals Density Functional Investigation of the Inclusion of Gold Clusters on a CH3S Self-Assembled Lattice on Au(111)

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Darnel J. Allen ◽  
Wayne E. Archibald ◽  
John A. Harper ◽  
John C. Saputo ◽  
Daniel Torres
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Theoretical Calculations ◽  
The Self ◽  
Au Clusters ◽  
Self Assembled ◽  
Functional Investigation ◽  
Small Clusters ◽  
The Impact ◽  
Insight Into

We employ first-principles density functional theoretical calculations to address the inclusion of gold (Au) clusters in a well-packed CH3S self-assembled lattice. We compute CH3S adsorption energies to quantify the energetic stability of the self-assembly and gold adsorption and dissolution energies to characterize the structural stability of a series of Au clusters adsorbed at the SAM-Au interface. Our results indicate that the inclusion of Au clusters with less than four Au atoms in the SAM-Au interface enhances the binding of CH3S species. In contrast, larger Au clusters destabilize the self-assembly. We attribute this effect to the low-coordinated gold atoms in the cluster. For small clusters, these low-coordinated sites have significantly different electronic properties compared to larger islands, which makes the binding with the self-assembly energetically more favorable. Our results further indicate that Au clusters in the SAM-Au interface are thermodynamically unstable and they will tend to dissolve, producing Au adatoms incorporated in the self-assembly in the form of CH3S-Au-SCH3 species. This is due to the strong S-Au bond which stabilizes single Au adatoms in the self-assembly. Our results provide solid insight into the impact of adatom islands at the CH3S-Au interface.

Theoretical predictions of structural electronic and optical properties of vanadium ferrite

2021 ◽  
pp. 2150387
Author(s):  
H. Bushra Munir ◽  
A. Afaq ◽  
Abu Bakar ◽  
Najm ul Aarifeen ◽  
Farid Ullah ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Lattice Constant ◽  
Density Functional ◽  
Theoretical Data ◽  
Cubic Phase ◽  
Temperature Sensitive ◽  
Electronic Density ◽  
Temperature Range ◽  
Theoretical Predictions ◽  
Conductivity Band

The structural properties of Vanadium Ferrite VFe2O4 are reported for temperature range 0–1000 K using Density Functional Theory. A comparative study with the available experimental and theoretical data in the literature is also presented. Effects of temperature on lattice constant, volume and bulk modulus are deduced that with the increase in temperature, bulk modulus decreases and lattice constant slightly increases. This proves that the material VFe2O4 remains in the same cubic phase for temperature range 0–1000 K. In addition, the optical response is observed with six optical constants like absorption, reflectivity, eloss, dielectric functions, refraction and optical conductivity. Band structures and electronic density of states are also computed by using TB-mBJ potential. We hope that our findings would provide a help to experimentalists in fabricating VFe2O4 for temperature-sensitive optical devices.

The structural parameters, structural stability and bulk modulus in RE2Sn2O7by first-principles calculations

2017 ◽  
Vol 31 (26) ◽  
pp. 1750184 ◽  
Author(s):  
C. G. Liu ◽  
J. Zhang ◽  
L. J. Chen ◽  
J. Wen ◽  
L. Y. Dong ◽  
...  
Keyword(s):  
Rare Earth ◽  
Bulk Modulus ◽  
Bond Length ◽  
Structural Stability ◽  
Density Functional ◽  
Structural Parameters ◽  
Structural Parameter ◽  
Functional Theory ◽  
Positional Parameter ◽  
Tight Connection

A systematic density functional theory study is performed to investigate the lattice parameters, the internal positional parameter [Formula: see text] and bond length of RE2Sn2O7(RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) pyrochlores. To analyze the structural stability in extreme conditions and verify whether bond strength varies inversely to bond length in rare-earth stannate pyrochlores, the structural parameter and bonding strength under hydrostatic pressure are studied. The tight connection between the different bond length contraction and the variation of 48[Formula: see text] oxygen positional parameter [Formula: see text] is also discovered. We calculated the bond length and the bulk modulus of RE2Sn2O7and found that the [Formula: see text]RE–O[Formula: see text] bond plays a predominant role in determining the bulk modulus. Meanwhile, the present calculations suggest that the “bimodal effect” also exists in rare-earth stannate pyrochlores.

The structure, elastic and thermodynamic properties of Ti2GaC from first-principles calculation

2019 ◽  
Vol 33 (06) ◽  
pp. 1950030 ◽  
Author(s):  
Xiao-Xia Pu ◽  
Xiao-Jiang Long ◽  
Lin Zhang ◽  
Jun Zhu
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constant ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Theoretical Data ◽  
Debye Model ◽  
First Principles Calculation

In this work, the structure, elastic and thermodynamic properties of Ti2GaC at high pressure (P) and high-temperature (T) are studied based on the density functional first-principles. The lattice parameters and elastic constants are well consistent with some theoretical data and experimental results. The elastic constant of Ti2GaC increase monotonously with the increase of pressure (P), which demonstrates the mechanical stability of Ti2GaC at the pressure (P) from 0 to 200 GPa. Mechanical properties including Poisson’s ratio ([Formula: see text]), Young’s modulus (E), shear modulus (G) and bulk modulus (B), which are obtained from elastic constants C[Formula: see text]. The ratio B/G value shows that Ti2GaC is a brittle material, but its enhancing ductility significantly with the elevate of pressure (P). The Grüneisen parameters ([Formula: see text]), thermal expansion coefficient ([Formula: see text]), heat capacity (C[Formula: see text]), elastic constant (C[Formula: see text]), bulk modulus (B), energy (E) and volume (V) with the change of temperature (T) or pressure (P) are calculated within the quasi-harmonic Debye model for pressure (P) and temperatures (T) range in 1600 K and 100 GPa. Besides, densities of states and energy band are also obtained and analyzed in comparison with available theoretical data.

First-principles investigation of structural, electronic, optical and dynamical properties in CsAu

Open Physics ◽  
2011 ◽  
Vol 9 (5) ◽  
Author(s):  
Bahattin Erdinc ◽  
Fethi Soyalp ◽  
Harun Akkus
Keyword(s):  
Bulk Modulus ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Electronic Band ◽  
Dynamical Properties ◽  
Energy Dependent

AbstractThe structural, electronic, optical and dynamical properties of CsAu compound in the CsCl(B2) phase were investigated using the density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant, static bulk modulus and first-order pressure derivative of the bulk modulus are reported and compared with previous experimental and theoretical calculations. The calculated electronic band structure for this compound is in good agreement with available theoretical and experimental studies. The present band calculation indicates that CsAu compound has an indirect gap at R→X points. Furthermore, the linear photon-energy-dependent dielectric functions have been calculated. For the first time, the electronic structure results are used, within the implementation of a linear-response technique, for calculations of phonon properties.

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