Determination of Silicon Electrical Properties Using First Principles Approach

Abstract Silicon nanowires have attracted attention as basis for reconfigurable electronics. However, as the size decreases, the electronic properties of the nanowires vary as a result of confinement, strain and crystal topology effects. Thus, at the thin diameter regime the band gap of Silicon nanowires can no longer be derived from a simple extrapolation of the isotropic bulk behaviour. This study compares band gap parameters in sub 10nm nanowires obtained from first-principles density-functional band structure calculations with extrapolations using continuum theory in order to rationalize the changes of the overall conductance, resistance and band gap. The device consists of silicon nanowire of size between 1 nm to 6nm. The results indicate an increase of, both the energy gap and the resistance along with reduced conductivity for the thinnest wires and a dependence on the crystal orientation with gaps reaching up to 4.3 eV along <111>, 4.0 eV along <110>, and 3.7 along <100>.

Download Full-text

Free Energy of Metals from Quasi-Harmonic Models of Thermal Disorder

Metals ◽

10.3390/met11020195 ◽

2021 ◽

Vol 11 (2) ◽

pp. 195

Author(s):

Pavel A. Korzhavyi ◽

Jing Zhang

Keyword(s):

Free Energy ◽

First Principles ◽

Density Functional ◽

Helmholtz Free Energy ◽

Complex Materials ◽

Predictive Capability ◽

Temperature Dependent ◽

Disordered Alloys ◽

Thermal Disorder ◽

Structure Calculations

A simple modeling method to extend first-principles electronic structure calculations to finite temperatures is presented. The method is applicable to crystalline solids exhibiting complex thermal disorder and employs quasi-harmonic models to represent the vibrational and magnetic free energy contributions. The main outcome is the Helmholtz free energy, calculated as a function of volume and temperature, from which the other related thermophysical properties (such as temperature-dependent lattice and elastic constants) can be derived. Our test calculations for Fe, Ni, Ti, and W metals in the paramagnetic state at temperatures of up to 1600 K show that the predictive capability of the quasi-harmonic modeling approach is mainly limited by the electron density functional approximation used and, in the second place, by the neglect of higher-order anharmonic effects. The developed methodology is equally applicable to disordered alloys and ordered compounds and can therefore be useful in modeling realistically complex materials.

Download Full-text

Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

Scientific Reports ◽

10.1038/s41598-021-86145-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Muhammad Faizan ◽

K. C. Bhamu ◽

Ghulam Murtaza ◽

Xin He ◽

Neeraj Kulhari ◽

...

Keyword(s):

Optical Properties ◽

Band Gap ◽

First Principles ◽

Density Functional ◽

Perovskite Solar Cells ◽

Dielectric Constants ◽

Maximum Efficiency ◽

Exchange Potential ◽

Double Perovskites ◽

Electronic And Optical Properties

AbstractThe highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

Download Full-text

Understanding the advantage of hexagonal WO3 as an efficient photoanode for solar water splitting: a first-principles perspective

Journal of Materials Chemistry A ◽

10.1039/c6ta03659g ◽

2016 ◽

Vol 4 (29) ◽

pp. 11498-11506 ◽

Cited By ~ 31

Author(s):

Taehun Lee ◽

Yonghyuk Lee ◽

Woosun Jang ◽

Aloysius Soon

Keyword(s):

Density Functional Theory ◽

Band Gap ◽

Water Splitting ◽

Anode Material ◽

First Principles ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Good Alternative ◽

Functional Theory ◽

Solar Water Splitting

Using first-principles density-functional theory calculations, we investigate the advantage of using h-WO3 (and its surfaces) over the larger band gap γ-WO3 phase for the anode in water splitting. We demonstrate that h-WO3 is a good alternative anode material for optimal water splitting efficiencies.

Download Full-text

Mono- and Bi-Molecular Adsorption of SF6 Decomposition Products on Pt Doped Graphene: A First-Principles Investigation

Applied Sciences ◽

10.3390/app8102010 ◽

2018 ◽

Vol 8 (10) ◽

pp. 2010 ◽

Cited By ~ 2

Author(s):

Yongqian Wu ◽

Shaojian Song ◽

Dachang Chen ◽

Xiaoxing Zhang

Keyword(s):

Single Molecule ◽

First Principles ◽

Density Functional ◽

Energy Gap ◽

Adsorption Parameters ◽

Functional Theory ◽

Decomposition Products ◽

Before And After ◽

Doped Graphene ◽

Sf6 Decomposition

Based on the first-principles of density functional theory, the SF6 decomposition products including single molecule (SO2F2, SOF2, SO2), double homogenous molecules (2SO2F2, 2SOF2, 2SO2) and double hetero molecules (SO2 and SOF2, SO2 and SO2F2, SOF2 and SO2F2) adsorbed on Pt doped graphene were discussed. The adsorption parameters, electron transfer, electronic properties and energy gap was investigated. The adsorption of SO2, SOF2 and SO2F2 on the surface of Pt-doped graphene was a strong chemisorption process. The intensity of chemical interactions between the molecule and the Pt-graphene for the above three molecules was SO2F2 > SOF2 > SO2. The change of energy gap was also studied and according to the value of energy gap, the conductivity of Pt-graphene before and after adsorbing different gas molecules can be evaluated.

Download Full-text

From Electronic Structure To Thermodynamics

MRS Proceedings ◽

10.1557/proc-104-13 ◽

1987 ◽

Vol 104 ◽

Cited By ~ 1

Author(s):

Giovanni B. Bachelet

Keyword(s):

First Principles ◽

Lattice Dynamics ◽

Density Functional ◽

Preliminary Test ◽

Computational Effort ◽

Consistent Theory ◽

Amorphous Systems ◽

Trajectory Approach ◽

Properties Of Materials

ABSTRACTA simple way to extend the remarkable results of Density Functional calculations to finite-temperature properties of materials is the quasi-harmonic theory of Lattice Dynamics. In this framework a thermodynamically consistent theory needs the complete phonon spectrum for a large periodic system (30–100 atoms/cell) at many different volumes, which poses severe practical limitations. In this paper I present the application to a semiconducting system of a method recently proposed by Bachelet and De Lorenzi to overcome these limitations. Based on low-temperature Molecular-Dynamics trajectories (now possible from first principles for semiconducting systems according to the method of Car and Parrinello), the method is shown to provide accurate dynamical matrices for an 8-atom silicon supercell. Such a successful, preliminary test, together with the fact that for larger and/or lower-symmetry systems the computational effort required by the “trajectory approach” is lower than traditional frozen-phonon or force-constant techniques, suggests its use in the determination of dynamical matrices of larger defect or amorphous systems, and thus in the study of their thermodynamics from first principles.

Download Full-text

First-Principles Determination of the Polarizabilities of Carbon Tubules as a Function of Length

MRS Proceedings ◽

10.1557/proc-349-241 ◽

1994 ◽

Vol 349 ◽

Cited By ~ 2

Author(s):

Andrew A. Quong ◽

Mark R. Pederson

Keyword(s):

First Principles ◽

Density Functional ◽

Valence Electron ◽

Local Density ◽

Density Approximation ◽

Functional Theory ◽

Size Dependent ◽

The Density Functional Theory ◽

Linear And Nonlinear

ABSTRACTWe use the local-density-approximation to the density-functional theory to determine the axial polarizabilities of fullerene tubules as a function of length and winding topologies. Specifically, we present linear polarizabilities for tubules of composition C12H24, C36H24, C40H20 and C60H24. The size-dependent variation in the dipole-coupled gaps between pairs of occupied and unoccupied levels leads to enhancements in the polarizability per valence electron as the length of the tubule increases. The results are compared to recent densityfunctional based calculations of the linear and nonlinear polarizabilities for fullerene and benzene molecules.

Download Full-text

First-principles study of solid methane at high pressure

BIBECHANA ◽

10.3126/bibechana.v12i0.11779 ◽

2014 ◽

Vol 12 ◽

pp. 70-79 ◽

Cited By ~ 1

Author(s):

Nurapati Pantha ◽

Jagaran Acharya ◽

Narayan Prasad Adhikari

Keyword(s):

High Pressure ◽

Band Gap ◽

First Principles ◽

Density Functional ◽

Wide Band ◽

Orthorhombic Structure ◽

Generalized Gradient ◽

Reported Data ◽

Quantum Espresso ◽

Solid Methane

We study the structural and electronic properties of solid methane of space group P212121 at high pressure. The density-functional theory (DFT) based first-principles calculations within the Generalized Gradient Approximations (GGA) have been performed by using Quantum Espresso package. Our findings show that the solid methane in orthorhombic structure compresses fast at the first, and then slowly as a function of elevated hydrostatic pressure. The pressure-volume diagram agrees with the available previously reported data up to pressure of around 200 GPa. In orthorhombic structure, solid methane is a wide band gap insulator at low pressures (tens of GPa). The band gap decreases with increase in the pressure. At high pressure (around 900 GPa), the band gap decreases to semi-conductor range (1.78 eV). Our results reveal that methane to be metallic above the pressure coverage of the present study which is consistent to the interior of the giant planets. The band gap as a function of pressure (from the present work) agrees well with the previously reported data. DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11779BIBECHANA 12 (2015) 70-79

Download Full-text

Ab Initio Electronic Structure Studies of CuO Multiferroics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.488-489.129 ◽

2012 ◽

Vol 488-489 ◽

pp. 129-132 ◽

Cited By ~ 3

Author(s):

C. Kanagaraj ◽

Baskaran Natesan

Keyword(s):

First Principles ◽

Density Functional ◽

Electronic Band Structure ◽

Metallic State ◽

Magnetic Ground State ◽

Electronic Band ◽

Functional Theory ◽

High Tc ◽

Band Structure Calculations ◽

Structure Calculations

We have performed detailed structural, electronic and magnetic properties of high - TC multiferroic CuO using first principles density functional theory. The total energy results revealed that AFM is the most stable magnetic ground state of CuO. The DOS and electronic band structure calculations show that in the absence of on-site Coulomb interaction (U), AFM structure of CuO heads to a metallic state. However, upon incorporating U in the calculations, a band gap of 1.2 eV is recovered. Furthermore, the Born effective charges calculated on Cu does not show any anomalous character.This suggests that the polarization seen in CuO could be attributed to the spin induced AFM ordering effect.

Download Full-text

A MOLECULAR DIODE BASED ON CONJUGATED CO-OLIGOMERS

International Journal of Nanoscience ◽

10.1142/s0219581x06004759 ◽

2006 ◽

Vol 05 (04n05) ◽

pp. 535-540

Author(s):

PING BAI ◽

CHEE CHING CHONG ◽

ER PING LI ◽

ZHIKUAN CHEN

Keyword(s):

Density Functional Theory ◽

Spatial Orientation ◽

First Principles ◽

Density Functional ◽

Infinite System ◽

Energy Gap ◽

Functional Theory ◽

Molecular Diode ◽

Current Voltage ◽

P Type

A molecular diode based on a conjugated co-oligomer composed of p-type and n-type segments is investigated using the first principles method. The co-oligomer is connected to Au electrodes to form an Au –oligomer– Au system. The infinite system is dealt with a finite structure confined in a device region and effects from semi-infinite electrodes. Density functional theory and nonequilibrium Green's function are used to describe the device region self-consistently. The current–voltage (I–V) characteristics of the constructed system are calculated and a rectification behavior is observed. The energy gap and the spatial orientation of molecular orbitals, and the transmission functions are calculated to analyze the I–V characteristics of the molecular diode.

Download Full-text

First-principles study on electronic, optic, elastic, dynamic and thermodynamic properties of RbH compound

International Journal for Simulation and Multidisciplinary Design Optimization ◽

10.1051/smdo/2015006 ◽

2015 ◽

Vol 6 ◽

pp. A6 ◽

Cited By ~ 5

Author(s):

Sinem Erden Gulebaglan ◽

Emel Kilit Dogan ◽

Mehmet Nurullah Secuk ◽

Murat Aycibin ◽

Bahattin Erdinc ◽

...

Keyword(s):

Thermodynamic Properties ◽

Band Gap ◽

Lattice Constant ◽

First Principles ◽

Density Functional ◽

Temperature Dependent ◽

Functional Theory ◽

Salt Structure ◽

Elastic Lattice ◽

Good Agreement

We performed first-principles calculations to obtain the electronic, optical, elastic, lattice-dynamical and thermodynamic properties of RbH compound with rock salt structure. The ground-state properties, i.e., the lattice constant and the band gap were investigated using a plane wave pseudopotential method within density functional theory. The calculated lattice constant, bulk modulus, energy band gap and elastic constants are reported and compared with previous theoretical and experimental results. Our calculated results and the previous results which are obtained from literature are in a good agreement. Moreover, real and imaginary parts of complex dielectric function, reflectivity spectrum, absorption, extinction coefficient and loss function as a function of photon energy and refractive index with respect to photon wavelength were calculated. In addition, temperature dependent thermodynamic properties such as Helmholtz free energy, internal energy, entropy and specific heat have been studied.

Download Full-text