Post by xg123 on Mar 5, 2012 14:28:18 GMT 7
Alkali halides have been extensively studied due to their crucial applications in scintillation detectors, photography, medicine and chemical business. It is also intriguing that they could possibly be used as prototype systems to test theoretical models, simply because they belong to compounds typical ironic. Their structural and electronic properties are the basis to explain properly linked optical and electrical phenomena, which are crucial for their applications. Nevertheless, couple of investigations have focused on their structural properties and density of electronic states. The theory of density functional has been extensively employed to study the properties with the ground state from the supplies, which could get the exact parameters with the structure although it generally underestimates the band gap. We currently utilised this method to study the structural and electronic properties of alkali halides. In this passage, our attention is paid only for sodium bromide simply because it really is representative for the other, and above all there is certainly adequate experimental and theoretical data, that are critical to verify our outcomes.
All calculations are performed inside the DFT-GGA as implemented in the ABINIT package, which can be depending on ab initio pseudopotentials and a basis set of plane wave. The pseudopotentials used are generated by the technique Trouiller-Martin, that is included inside the code FHI98PP. The valence electrons for Na and Br are deemed and 3s1 4s24p5, respectively. The Perdew-Burke-Ernzerh (PBE) function is employed to reflect the exchange-correlation power, and the technique of conjugate gradient minimization algorithms for a self-consistent field (SCF) cycles. Two parameters that considerably have an effect on the accuracy and time with the calculation are the cutoff power of plane wave and the special k point grid. To correctly choose the two parameters, we initial perform a series of convergence tests. In our function, the cutoff energy is 25 Ha for all instances, and the specific k points sampling integration over the Brillouin zone are employed using the Monkhorst-Pack approach with 6 with 6 ¡Á 6 ¡Á 6 special k -point mesh.
Sodium bromide(7647-15-6) belongs for the group Fm-3m space (225) and each and every primitive cell consists of two atoms with atomic positions of Na+ ions at (0,0,0) and Br-ions (0.5,0.5,0.5 ). Before calculating the electronic structure, the optimal geometric structure is made to find the equilibrium values from the lattice constants a. For calculating structural relaxation, we change the lattice constants close to the declared worth, then calculate the total energy E for different values ??from the unit cell volume V. The volume with the cell balancing unit V0, bulk modulus B0 and its pressure derivative B00 (ie, dB / dP) are obtained by fitting the calculated data for the third order Birch-Murnaghan equation of state ( EOS), exactly where E0 and V are the total power balance and also the volume of unit cell, respectively. It really should be noted that great agreement is obtained on the volume of unit cell varied. The network equipped continuous, bulk modulus, its derivative and pressure are a = 6.02MA, B0 = 193.64 kbar, and B00 = three.84, respectively. Our calculated worth in the lattice continual is 0.84% bigger than the experimental 1 (five.97MA). Thomas and Shanker also studied the modulus with the sodium bromide employing the Birch equation of state (BES), which was derived from the theory of finite deformation. Their results show that B0 and B00 are 199 kbar and five.46, respectively. As a result, our result is virtually exactly the same as the experimental value of B0 (195 kbar) and far more accurate.
It could be seen that sodium bromide is direct gap insulator with all the valence band maximum (VBM) and conduction band minimum (CBM) in theapproach. Our calculated lattice continual balance is 0.84% higher than the experimental value, along with the bulk modulus and its pressure derivatives are in almost exactly the same because the reported data. Sodium bromide The band structures, DOS and PDOS are presented, and outcomes had been discussed and compared with obtainable experimental data and theoretical.
This post is reproduced from guidechem.com www.guidechem.com
All calculations are performed inside the DFT-GGA as implemented in the ABINIT package, which can be depending on ab initio pseudopotentials and a basis set of plane wave. The pseudopotentials used are generated by the technique Trouiller-Martin, that is included inside the code FHI98PP. The valence electrons for Na and Br are deemed and 3s1 4s24p5, respectively. The Perdew-Burke-Ernzerh (PBE) function is employed to reflect the exchange-correlation power, and the technique of conjugate gradient minimization algorithms for a self-consistent field (SCF) cycles. Two parameters that considerably have an effect on the accuracy and time with the calculation are the cutoff power of plane wave and the special k point grid. To correctly choose the two parameters, we initial perform a series of convergence tests. In our function, the cutoff energy is 25 Ha for all instances, and the specific k points sampling integration over the Brillouin zone are employed using the Monkhorst-Pack approach with 6 with 6 ¡Á 6 ¡Á 6 special k -point mesh.
Sodium bromide(7647-15-6) belongs for the group Fm-3m space (225) and each and every primitive cell consists of two atoms with atomic positions of Na+ ions at (0,0,0) and Br-ions (0.5,0.5,0.5 ). Before calculating the electronic structure, the optimal geometric structure is made to find the equilibrium values from the lattice constants a. For calculating structural relaxation, we change the lattice constants close to the declared worth, then calculate the total energy E for different values ??from the unit cell volume V. The volume with the cell balancing unit V0, bulk modulus B0 and its pressure derivative B00 (ie, dB / dP) are obtained by fitting the calculated data for the third order Birch-Murnaghan equation of state ( EOS), exactly where E0 and V are the total power balance and also the volume of unit cell, respectively. It really should be noted that great agreement is obtained on the volume of unit cell varied. The network equipped continuous, bulk modulus, its derivative and pressure are a = 6.02MA, B0 = 193.64 kbar, and B00 = three.84, respectively. Our calculated worth in the lattice continual is 0.84% bigger than the experimental 1 (five.97MA). Thomas and Shanker also studied the modulus with the sodium bromide employing the Birch equation of state (BES), which was derived from the theory of finite deformation. Their results show that B0 and B00 are 199 kbar and five.46, respectively. As a result, our result is virtually exactly the same as the experimental value of B0 (195 kbar) and far more accurate.
It could be seen that sodium bromide is direct gap insulator with all the valence band maximum (VBM) and conduction band minimum (CBM) in theapproach. Our calculated lattice continual balance is 0.84% higher than the experimental value, along with the bulk modulus and its pressure derivatives are in almost exactly the same because the reported data. Sodium bromide The band structures, DOS and PDOS are presented, and outcomes had been discussed and compared with obtainable experimental data and theoretical.
This post is reproduced from guidechem.com www.guidechem.com