Kulwinder Kaur

Kinetic and equilibrium studies on the removal of Cd2+ ions from water using polyacrylamide grafted rice (Oryza sativa) husk and (Tectona grandis) saw dust.

The increase in the use of heavy metals has resulted in an increased flux of metallic substances into the aquatic environment which poses a danger to human health. The present work relates to the removal of cadmium ions by treatment with polyacrylamide grafted rice (Oryza sativa) husk/saguan (Tectona grandis) saw dust. The drinking water guideline value recommended by WHO for cadmium is 0.005 ppm.The adsorbent has been prepared by treatment of rice husk/saw dust with acrylamide. Removal has been studied at various pH values for different times of contact and adsorbate concentrations and is found to be pH-dependent, maximum removal occurs at pH 9 and at a contact time of 180 min for both the adsorbents. The results were found to be consistent with both the Langmuir and Freundlich isotherm models. The value of n (rate constant) determined at pH 9 has been found to be 1 (within experimental limits). This is further substantiated by applying the Lagergren model. The intra-particle diffusion constants were determined by the Morris-Weber model. Continuous flow column studies have also been undertaken and the breakthrough characteristics were determined. Desorption has been affected with 0.5M HCl. The results suggest that both polyacrylamide grafted rice husk/saw dust can be used as efficient and cost effective adsorbents for cadmium ion removal.

Effect of pressure on electronic and thermoelectric properties of magnesium silicide: A density functional theory study*

We study the effect of pressure on electronic and thermoelectric properties of Mg2Si using the density functional theory and Boltzmann transport equations. The variation of lattice constant, band gap, bulk modulus with pressure is also analyzed. Further, the thermoelectric properties (Seebeck coefficient, electrical conductivity, electronic thermal conductivity) have been studied as a function of temperature and pressure up to 1200 K. The results show that Mg2Si is an n-type semiconductor with a band gap of 0.21 eV. The negative value of the Seebeck coefficient at all pressures indicates that the conduction is due to electrons. With the increase in pressure, the Seebeck coefficient decreases and electrical conductivity increases. It is also seen that, there is practically no effect of pressure on the electronic contribution of thermal conductivity. The paper describes the calculation of the lattice thermal conductivity and figure of merit of Mg2Si at zero pressure. The maximum value of figure of merit is attained 1.83×10−3 at 1000 K. The obtained results are in good agreement with the available experimental and theoretical results.

First principle investigation of the electronic and thermoelectric properties of Mg2C

In this paper, electronic and thermoelectric properties of Mg2C are investigated by using first principle pseudo potential method based on density functional theory and Boltzmann transport equations. We calculate the lattice parameters, bulk modulus, band gap and thermoelectric properties (Seebeck coefficient, electrical conductivity, and thermal conductivity) of this material at different temperatures and compare them with available experimental and other theoretical data. The calculations show that Mg2C is indirect band semiconductor with a band gap of 0.75 eV. The negative value of Seebeck coefficient shows that the conduction is due to electrons. The electrical conductivity decreases with temperature and Power factor (PF) increases with temperature. The thermoelectric properties of Mg2C have been calculated in a temperature range of 100 K–1200 K.

TiPdSn: A half Heusler compound with high thermoelectric performance

The electronic, structural and thermoelectric properties of TiPdSn half Heusler material have been studied using density functional theory and semi classical Boltzmann transport theory. It has been found that TiPdSn is an indirect band gap semiconductor with band gap 0.48 eV. TiPdSn exhibits large power factor for p-type composition which is equal to 14.88 × 1011 W/msK2 at 700 K. The lattice thermal conductivity and relaxation time decrease with an increase in temperature. To analyze the stability of this compound, phonon properties like phonon dispersion, phonon density of states and heat capacity have been calculated. The maximum value of ZT, which is equal to 0.74, is attained at 500 K.

Structural, electronic, mechanical, and thermoelectric properties of a novel half Heusler compound HfPtPb

We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semi-classical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Youngs modulus, elastic constants, Poissons ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pughs ratio and Frantsevichs ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conducti...

Thermoelectric properties of ZrNiSn Half-Heusler system: An ab-initio study

In this work, we have studied the thermoelectric properties of ZrNiSn system using the density functional theory and Boltzmann transport equations. Thermoelectric properties of this system have been calculated in 100-1200K temperature range. The negative value of seebeck coefficient of this system indicates that conduction is due to the electrons. Upto 1000K, the electrical conductivity decreases with increase in the temperature. While, the electronic thermal conductivity increases with increase in the temperature. The maximum power factor is attained at 1000K which is equal to 4×1011V2SK−2ms.

Effect of hydrostatic pressure on the structural and electronic properties of Cd0.75Cr0.25S

In this paper we present the results obtained from first principle calculations of the effect of hydrostatic pressure on the structural and electronic properties of Cd1-xCrxS diluted magnetic semiconductor in Zinc Blende (B3) phase at x=0.25. High pressure behavior of Cd1-xCrxS has been investigated between 0 GPa to100 GPa The calculations have been performed using Density functional theory as implemented in the Spanish Initiative for Electronic Simulations with Thousands of Atoms code using local density approximation as exchange-correlation (XC) potential. Calculated electronic band structures of Cd1-xCrxS are discussed in terms of contribution of Cr 3d5 4s1, Cd 4d10 5s2, S 3s2 3p4 orbital’s. Study of band structures shows half-metallic ferromagnetic nature of Cd0.75Cr0.25S with 100% spin polarization. Under application of external pressure, the valence band and conduction band are shifted upward which leads to modification of electronic structure

Ab-initio study of thermoelectric properties of Mg2Ge

In this paper we investigate the thermoelectric properties of Mg2Ge material using first principles pseudo potential method based on density functional theory and Boltzmann transport equations. The calculations show n-type conduction, indicating that the electrical conduction is due to electron. The electrical conductivity decrease with temperature; the negative value of Seebeck Coefficient also shows that the conduction is due to electron. In this paper we have calculated Seebeck coefficient, electrical conductivity and thermal conductivity. The thermoelectric properties of system have been calculated in this temperature range 100K-1200K. The value of Figure of Merit (ZT) of this material is also increasing with temperature and maximum value is 4.58×10−5.

Cd0.9375Mn0.0625S diluted magnetic semiconductor: A DFT study

We studied the spin polarized electronic band structures and magnetic properties of the diluted magnetic semiconductor Cd1-xMnxS in Zinc Blende phase (B3) with 0.0625 Mn by using ab initio method. The calculations were performed by using Density Functional Theory as implemented in the Spanish Initiative for Electronic Simulations with Thousands of Atoms code using local density approximation (LDA). Calculated electronic band structures and magnetic properties of Cd1-xMnxS are discussed in terms of contribution of Mn 3d5 4s2, Cd 4d10 5s2, S 3s2 3p4 orbitals. The total magnetic moment is found to be 5.00 µb for Cd1−xMnxS at x=0.0625. This value indicate that Mn atom adds no hole carrier to the perfect CdS crystal. We found that Mn doped systems are ferromagnetic. Calculated results are in good agreement with previous studies.

Thermoelectric properties of Al doped Mg2Si material

In the present paper we have calculated thermoelectric properties of Al doped Mg2Si material (Mg2−xAlxSi, x=0.06) using Pseudo potential plane wave method based on DFT and Semi classical Boltzmann theory. The calculations showed n-type conduction, indicating that the electrical conduction are due to electron. The electrical conductivity increasing with increasing temperature and the negative value of Seebeck Coefficient also show that the conduction is due to electron. The thermal conductivity was increased slightly by Al doping with increasing temperature due to the much larger contribution of lattice thermal conductivity over electronic thermal conductivity.