First-Principles Equation of State for an Energetic Intermetallic Mixture

2003 ◽  
Vol 800 ◽  
Author(s):  
X. Lu ◽  
S. Hanagud
Keyword(s):  
Equation Of State ◽  
Density Functional ◽  
Generalized Gradient ◽  
Phonon Modes ◽  
Functional Theory ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory ◽  
Ab Initio Prediction ◽  
Shock Hugoniot ◽  
Mixture Theories

AbstractThe thermodynamically complete equation of state P=P(ρ,T) for a intermetallic mixture of nickel and aluminum is obtained via first principle calculations for pressures up to 300GPa and temperatures up to 1000K. The calculations for the static-lattice EOS are carried out in the framework of the density functional theory (DFT), using generalized gradient approximations and ultrasoft psuedopotentials. The phonon modes are calculated by using the density functional perturbation theory (DFPT). First, the EOS for each species is obtained based on ab initio prediction of the electron ground state and thermal excitations. Then, the mixture theories are utilized to obtain the EOS for the mixture. Two mixture theories are proposed, which correspond to the two limiting cases. The nature of the real mixture is intermediate to those of the two idealized mixtures and hence can be modeled as a weighted combination of the two cases. The Comparisons of the EOS for nickel and aluminum obtained from existing shock Hugoniot data show good agreement with the theoretical results.

scholarly journals Structural and piezoelectric coefficients of AlP under pressure

2018 ◽  
Vol 6 (2) ◽  
pp. 53
Author(s):  
Salah Daoud ◽  
Rabie Mezouar ◽  
Abdelfateh Benmakhlouf
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Generalized Gradient ◽  
Aluminum Phosphide ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Zinc Blende ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory

The present work aims to investigate the structural parameters and the piezoelectric coefficients of cubic zinc-blende Aluminum phosphide (AlP) under high pressure up to 21 GPa, using plane wave-pseudopotential (PW-PP) approach in the framework of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the generalized gradient approximation (GGA) for the exchange-correlation functional. The results obtained are analyzed and compared with other data of the literature. The structural parameters and the piezoelectric coefficients calculated here agree well with other data of the literature. We found also that both the direct and converse piezoelectric coefficients increase with increasing pressure up to 21 GPa. 

scholarly journals The Case Studies of PtX2 (X = As, P) as High Thermo-power Materials

2021 ◽  
pp. 26-36
Author(s):  
Adewumi I. Popoola ◽  
Adebayo T. Adepoju
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Phonon Dispersion ◽  
Material Selection ◽  
Low Frequency ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory ◽  
Bending Modes

For thermoelectric applications, semiconductors are generally better than metals and insulators. PtAs2 and PtP2 are indirect energy gap semiconductors that have been predicted with high thermo-powers (PtP2 having higher thermopower than PtAs2). The crystal structure and the electronic structure of PtAs2 and PtP2 are similar except for the energy band gap of PtP2 that is wider than that of PtAs2. The generalized gradient approximation of the Density Functional Theory (DFT), the Density Functional Perturbation Theory (DFPT) were used to explore the full elastic tensors, phonon dispersion and the thermodynamics of PtP2 and PtAs2. This was done to understand the link, if any, between high thermo-power materials and the results. The two compounds are dynamically and elastically stable with higher mechanical properties recorded for PtP2 over PtAs2. The calculated entropy, vibration free energy and the heat capacity at constant volume for PtAs2 (PtP2) were 354.51 (264.18) J/K; -9.21 (27.84) kJ and 276.04 (250.36) J/K at 300 K respectively. The low frequency acoustic modes are between 100 - 170 cm-1 for PtAs2 while it is between100 - 190 cm-1 for PtP2. The calculated high frequency transverse optical (TO) mode for PtP2 is 410 cm-1 while it is 250 cm-1 for PtAs2.  Further analysis of the phonons spectrum showed that additional bond-bending modes can be created in PtP2 than in PtAs2.  All the results points toward PtP2 as better material over PtAs2 for thermoelectric application and these, with or without the knowledge of the energy bandgap can serve to guide material selection/modelling.

Structural and Vibrational Properties of FeO Using First-Principles

2013 ◽  
Vol 665 ◽  
pp. 49-52
Author(s):  
Nisarg K. Bhatt ◽  
A.B. Patel ◽  
A.Y. Vahora ◽  
P.R. Vyas ◽  
B.Y. Thakore ◽  
...  
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Vibrational Properties ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Equation Of States ◽  
Pseudopotential Calculations ◽  
The Density Functional Theory ◽  
Shock Hugoniot

We have studied the equation of states and vibrational properties of FeO using DFT based plane-wave pseudopotential (PW-DFT) within the generalized gradient approximation. The calculated cohesive properties at ambient condition, namely, lattice constant (a0), bulk modulus (B0) and its first pressure derivative (), are reported for B1-phase of FeO, in agreement with previous experimental and other theoretical results. A linear-response approach to the density functional theory was used to derive the phonon frequencies and phonon density of state (p-dos). Further, in order to calculate both static and dynamic equations of states, nearest-neighbour second-moment tight-binding energy model (TB-SMA) was used. Parameters of the present TB-SMA model were determined by the presentab initiopseudopotential calculations. It is found that the present simple TB-SMA scheme is able to mimic shock Hugoniot for such oxides correctly.

scholarly journals EOS parameters and elastic properties of cubic rock-salt BP

2019 ◽  
Vol 7 (1) ◽  
pp. 7
Author(s):  
Salah DAOUD
Keyword(s):  
Elastic Properties ◽  
Density Functional ◽  
Young Modulus ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Boron Phosphide ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory ◽  
Aggregate Material ◽  
Good Agreement

The present work aims to study the equation of state (EOS) under compression up to 100 GPa, and the elastic properties of cubic rocksalt Boron phosphide (BP) material. The EOS parameters and the elastic constants of our material of interest were predicted using plane wave-pseudopotential (PW-PP) approach in the framework of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the generalized gradient approximation (GGA) for the exchange-correlation functional. The Young modulus, the Poisson's ratio, the sound velocity, the Debye temperature and the melting temperature of the aggregate material were also presented. The results obtained are in general in good agreement compared to other data of the literature.

scholarly journals Measuring the structure and equation of state of polyethylene terephthalate at megabar pressures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Lütgert ◽  
J. Vorberger ◽  
N. J. Hartley ◽  
K. Voigt ◽  
M. Rödel ◽  
...  
Keyword(s):  
Equation Of State ◽  
Polyethylene Terephthalate ◽  
Density Functional ◽  
Equations Of State ◽  
Md Simulations ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Shock Hugoniot ◽  
Highly Correlated

AbstractWe present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, $$({\hbox {C}}_{10} {\hbox {H}}_8 {\hbox {O}}_4)_n$$ ( C 10 H 8 O 4 ) n , also called mylar) shock-compressed to ($$155 \pm 20$$ 155 ± 20 ) GPa and ($$6000 \pm 1000$$ 6000 ± 1000 ) K using in situ X-ray diffraction, Doppler velocimetry, and optical pyrometry. Comparing to density functional theory molecular dynamics (DFT-MD) simulations, we find a highly correlated liquid at conditions differing from predictions by some equations of state tables, which underlines the influence of complex chemical interactions in this regime. EOS calculations from ab initio DFT-MD simulations and shock Hugoniot measurements of density, pressure and temperature confirm the discrepancy to these tables and present an experimentally benchmarked correction to the description of PET as an exemplary material to represent the mixture of light elements at planetary interior conditions.

An Investigation of Half-Metallic Ferromagnets Behavior in Hg2CuTi-Type Heusler Alloy Ti2FeAl by Using GGA

2012 ◽  
Vol 535-537 ◽  
pp. 1291-1294 ◽  
Author(s):  
Xiu De Yang ◽  
Bo Wu ◽  
Song Zhang
Keyword(s):  
Density Functional Theory ◽  
Heusler Alloy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Half Metallic ◽  
Generalized Gradient Approximation ◽  
Indirect Exchange ◽  
The Density Functional Theory ◽  
Direct Hybridization

By using generalized gradient approximation (GGA) scheme within the density functional theory (DFT), the electronic and magnetic properties of Hg2CuTi-type Heusler alloy Ti2FeAl were investigated. The results reveal that a 100% spin polarization appears at Fermi level (εF) in Ti2FeAl, and is maintained during lattice range of 5.1Å~6.2Å. Ti2FeAl is one of stable Half-Metallic Ferromagnets (HMF) with a spin-minority gap of 0.5 eV at εF and total magnetic moment of 1μB per unit cell. Our studies also indicate that the competition between RKKY-type indirect exchange and direct hybridization of d-electronic atoms plays a dominating role in determining the magnetism.

scholarly journals Oxygen vacancy and doping atom effect on electronic structure and optical properties of Cd2SnO4

RSC Advances ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 640-646 ◽  
Author(s):  
Mei Tang ◽  
JiaXiang Shang ◽  
Yue Zhang
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
La Doped ◽  
Doping Atom ◽  
Atom Effect

The electronic structure and optical properties of oxygen vacancy and La-doped Cd2SnO4 were calculated using the plane-wave-based pseudopotential method based on the density functional theory (DFT) within the generalized gradient approximation (GGA).

STRUCTURE AND MAGNETIC PROPERTIES OF Co12X(X = Ni, Ag, Pt, Au) CLUSTERS

2007 ◽  
Vol 21 (30) ◽  
pp. 5091-5098 ◽  
Author(s):  
Q. L. LU ◽  
J. C. JIANG ◽  
J. G. WAN ◽  
G. H. WANG
Keyword(s):  
Density Functional ◽  
Magnetic Moments ◽  
Stable Configuration ◽  
Many Body ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Au Clusters ◽  
The Density Functional Theory ◽  
Ground State Structures ◽  
Body Potential

The ground state structures of Co 12 X ( X = Ni , Ag , Pt , Au ) clusters are obtained by a genetic algorithm with a Gupta-like many-body potential, and further optimized using the density functional theory with generalized gradient approximation. The structures of Co 12 X have a slightly distorted icosahedral pattern. The X atom is on the surface for the most stable configuration. Their total magnetic moments are 0μ B , 3μ B , 21μ B , and 22μ B , respectively. The reasons for the reduction of magnetism of Co 12 X are discussed in detail.

MAGNETIC MAP OF MnNi ALLOYED MONOLAYER ON Cu(001) SUBSTRATE: AB-INITIO CALCULATIONS

2010 ◽  
Vol 09 (06) ◽  
pp. 619-622
Author(s):  
BOTHINA A. HAMAD
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Exchange Correlation Potential ◽  
The Density Functional Theory ◽  
Correlation Potential

In this work, a theoretical study of the structural, electronic and magnetic properties are presented for Mn 0.5 Ni 0.5 alloyed overlayer adsorbed on Cu (001) surface. The calculations were performed using the density functional theory (DFT) and the exchange-correlation potential was treated by the generalized gradient approximation (GGA). The system was fully relaxed except for the central layer, which yields to outward relaxations and inward Mn and Ni surface atoms, respectively in the ferromagnetic and antiferromagnetic configurations. The in-plane ferromagnetic configuration was found to be more stable than the antiferromagnetic one by 25 meV/atom. The local magnetic moments of Mn atoms were found to be about 4 μ B , whereas those of the Ni atoms where found to be 0.46 μ B .

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