Papers by Muhammad Rijalul Huda
Journal of Applied Physics, 2012
ABSTRACT Using first-principles density-functional theory, we have investigated the intrinsic and... more ABSTRACT Using first-principles density-functional theory, we have investigated the intrinsic and extrinsic doping properties of CoAl2O4 by calculating the transition energies and formation energies of intrinsic and extrinsic defects. We find that CoAl2O4 exhibits strong asymmetrical doping properties: Although excellent p-type conductivity can be achieved by Li or Na doping at O-rich growth condition, n-type conductivity cannot be achieved by any intrinsic or extrinsic dopants at any growth conditions. These asymmetrical doping properties are attributed to the formation of intrinsic defects, particularly AlCo, which has very low formation energy at all growth conditions. Our results suggest that for better use of CoAl2O4, the electronic devices should require CoAl2O4 to exhibit p-type conductivity.
Asian Social Science, 2017
The purpose of this research is to get deep meaning of policy implementation to improve quality o... more The purpose of this research is to get deep meaning of policy implementation to improve quality of primary education teachers in Laos and Indonesia. Research locations are in the Ministry of Education in those both countries. This research used a qualitative approach with a multi-case study design. First, policy formulation consider the aspect of novelty and national education goals; second, policy dissemination of existing policies do after getting approval from parliament, as well as socialization is done to the department of education in each provinces and districts; third, policy implementation process is done by establishing a monitoring team to oversee that the policy can work well; fourth, monitoring and evaluation of the implementation is done periodically, at least every six months, and the results of the evaluation are reported to the Ministry; fifth, gaps in the policy implementation is because monitoring can not be run with maximum caused by geographical conditions and t...
Lanthanide-borides show antiferromagnetic behavior where the magnetocrystalline anisotropy plays ... more Lanthanide-borides show antiferromagnetic behavior where the magnetocrystalline anisotropy plays a major role in their magnetic structures. A recent neutron scattering experiment showed a particular noncollinear behavior of GdB 4 at room temperature. We will present our study on the non-collinear magnetism of GdB 4 with the GGA + U method with spin orbit coupling. We have found that with or without spin-orbit coupling and with U collinear magnetism is favorable by few meV than the experimentally found noncollinear magnetic configuration. Among the noncollinear magnetism configurations that we have studied, when a U parameter and spin-orbit coupling are considered, the experimentally found noncollinear configuration was found to be favorable. However, the value of U parameter is not unique; a range of values were able to get this magnetic order.
As a part of our ongoing research efforts in theoretical studies of coinage metal clusters, we re... more As a part of our ongoing research efforts in theoretical studies of coinage metal clusters, we report here results of ab initio electronic structure computations for small neutral, cationic and anionic silver (Agn, n=2â€''4) clusters. The effects of correlation have been studied by using the techniques of many body perturbation theory and coupled cluster theory whereas relativistic effects have been
Journal of Materials Chemistry A, 2013
ABSTRACT It is known that the stability of GaP as a photocatalyst in electrolytes can be enhanced... more ABSTRACT It is known that the stability of GaP as a photocatalyst in electrolytes can be enhanced by nitrogen doping, GaP:N. However, both GaP (indirect gap) and GaP:N (direct gap) have poor optical absorption properties across their fundamental band gap. To enhance optical absorption as well as the photocurrent, we have examined by density functional theory the favorability of oxygen and hydrogen impurities in conjunction with N doping in bulk GaP. It has been found here that O-related defects are more favorable, whereas H with N substitution is not very favorable. These O–N related defects create a global effect in the GaP lattice by both volume and band gap reduction. Enhancement of optical absorption was also found due to these types of complex doping.
Solar Hydrogen and Nanotechnology V, 2010
Efficient photo-electrochemical (PEC) splitting of water to hydrogen usually requires photoelectr... more Efficient photo-electrochemical (PEC) splitting of water to hydrogen usually requires photoelectrodes to have certain electronic properties. Unfortunately, at present available semiconductors do not meet all these criteria. So, a thorough understanding of band-engineering for mixed alloys is necessary to successfully design these photoelectrodes. Among the semiconductors, transition metal oxides are of particular interest due to their low cost and relatively high stability in aqueous media. Here, we will present a theoretical study of delafossite-alloys for PEC photo-electrodes. Previous studies have indicated that the group IIIA delafossite family (CuMO 2 , M = Al, Ga, In) do not exhibit direct band gaps. Their fundamental band gaps are significantly smaller than their reported optical band gaps. On the other hand group IIIB delafossite family (CuMO 2 , M = Sc, Y, La) in general show direct band gaps and, except for CuLaO 2 , band gaps are above 3.00 eV. However, both of these two families exhibit p-type conductivity. We will show that by appropriate alloying of these two delafossite-families we can tune their band gaps and other opto-electronic properties. These types of alloying are desirable, as these introduce no localized impurity states in the band gap due to isovalent alloying. Also, the electronic effective masses can be lowered by selective doping of main group elements. Finally, it will be discussed that, lowering the symmetry constraints of these alloys would enhance their optical absorption properties. We'll also discuss that alloying with other 3d metal elements may decrease the band gap, but would increase the effective masses of the photo-electrons.
Physical Review B, 2009
An unconventional spin-Peierls-type distortion was found in a nonmagnetic atom N doped pseudo-one... more An unconventional spin-Peierls-type distortion was found in a nonmagnetic atom N doped pseudo-onedimensional WO 3 system. The periodicity of the initial ferromagnetic WO 3 : N is doubled in one direction, and the band gap opens up due to this distortion. The magnetic moment at the N site is asymmetric in the distorted system, and the interaction between the localized spin is very weak. We show that the large exchange interaction of the nitrogen 2p atomic orbital and the pseudo-one-dimensional W-O-W chain in monoclinic WO 3 structure is the origin of this spin-Peierls-like transition that leads to the stabilization of an unusual negative-U charge-ordered system.
Physical Review B, 2008
ZnO and GaN have a type-II band offset. The incorporation of one compound into the other would le... more ZnO and GaN have a type-II band offset. The incorporation of one compound into the other would lead to a reduced bandgap as compared to that of either ZnO or GaN. Our density-functional theory calculation reveals an asymmetric bandgap reduction in this nonisovalent system; i.e., incorporating GaN in a ZnO host results in a much more effective bandgap reduction than incorporating ZnO in a GaN host. We further find that the random-alloy system is more favorable than the superlattice system in terms of light absorption in the longerwavelength regions. Our results suggest that the wave-function localization at the band edges plays an important role in how to choose the host material and dopant for effective bandgap engineering through semiconductor compound alloying.
Physical Review B, 2006
Here we have studied hydrogen molecule adsorption on small platinum clusters. The generalized gra... more Here we have studied hydrogen molecule adsorption on small platinum clusters. The generalized gradient approximation to density functional theory has been used and spin-orbit coupling was included selfconsistently. In general, dissociative adsorption of a hydrogen molecule on a top site was found common for all sizes of platinum clusters considered here. To study charging effects on H 2 adsorption, calculations of relaxed H 2 Pt n − were performed. Multiple hydrogen adsorptions were also considered, which show an interesting dependency on the cluster size.
Physical Review A, 2006
We have shown that spin-orbit coupling plays an important role in determining the structures of p... more We have shown that spin-orbit coupling plays an important role in determining the structures of platinum nanoclusters. We have used spin-orbit coupling self-consistently with density functional theory to study the geometry of platinum clusters and their binding energy. It has been found that the relative energies of the isomers of a cluster of a given size can be changed due to the inclusion of spin-orbit coupling. Planar structures were found for Pt n clusters with n ഛ 5.
Double numerical basis set and the DMol3 suite of programs were used to study the surface propert... more Double numerical basis set and the DMol3 suite of programs were used to study the surface properties of thin film slabs up to nine layers for thorium (100) and (111) surfaces. The calculations were done in the generalized gradient approximation (GGA) of density functional theory (DFT), with the Perdew and Wang functional. No geometry optimizations were performed. We will present the work functions and surface energy of each slab and discuss the quantum size effects. Results will be compared with similar results for other systems. * Work supported in part by the Welch Foundation, Houston, Texas (Grant No. Y-1525)
Journal of Physics: Condensed Matter, 2012
(Ga, N) cluster-doping in ZnO has been considered as a valid approach to enhance the p-type dopin... more (Ga, N) cluster-doping in ZnO has been considered as a valid approach to enhance the p-type doping of ZnO. So far, the argument on the enhancement is based on the reduction of dopant formation energy and ionization energy. Here we present spin-polarized density functional theory calculation to reveal that in (Ga, N) cluster doping of ZnO, a hole state created by a (Ga, N) cluster contains the contribution from all N atoms in the cluster, meaning a more delocalized nature of the hole as compared to the case of mono N doping of ZnO. Our results explain from the electronic point of view why (Ga, N) cluster doping enhances the p-type doping of ZnO. We will compare both LDA+U and hybrid density functional calculations.
Journal of Physical Organic Chemistry, 1997
Skip to Main Content. ... Research Article. Density functional calculations of the influence of s... more Skip to Main Content. ... Research Article. Density functional calculations of the influence of substitution on singlettriplet gaps in carbenes and vinylidenes. Sharon E. Worthington,; Chistopher J. Cramer. Article first published online: 4 DEC 1998. ...
Atomic hydrogen and oxygen adsorptions on delta -Pu (100) and (111) surfaces have been investigat... more Atomic hydrogen and oxygen adsorptions on delta -Pu (100) and (111) surfaces have been investigated using the generalized gradient approximation of density functional theory with Perdew and Wang functionals. For the (100) surface, the center position of adatom is found to be the most favorable site with the normal distance of hydrogen or oxygen to the surface being the minimum. For the (111) surface, the center position is also the preferred site, but with lower chemisorption energy compared to the (100) center site. The 5f orbitals are found to be delocalized, specifically as one approaches the Fermi level. The coordination numbers play a significant role in the chemical bonding process. Mulliken charge distribution analysis indicates that the interaction of Pu with H or O mainly takes place in the first layer, with the other two layers being only slightly affected. The ionic part of bonding is found to be rather more prominent in oxygen adsorption. Work functions, in general, tend...
Journal of Applied Physics, 2010
We present a density-functional theory study on the electronic structure of pure and 3d transitio... more We present a density-functional theory study on the electronic structure of pure and 3d transition metal ͑TM͒ ͑Sc, Ti, Cr, Mn, and Ni͒ incorporated ␣-Fe 2 O 3. We find that the incorporation of 3d TMs in ␣-Fe 2 O 3 has two main effects such as: ͑1͒ the valence and conduction band edges are modified. In particular, the incorporation of Ti provides electron carriers and reduces the electron effective mass, which will improve the electrical conductivity of ␣-Fe 2 O 3. ͑2͒ The unit cell volume changes systematically such as: the incorporation of Sc increases the volume, whereas the incorporation of Ti, Cr, Mn, and Ni reduces the volume monotonically, which can affect the hopping probability of localized charge carriers ͑polarons͒. We discuss the importance of these results in terms of the utilization of hematite as a visible-light photocatalyst.
Journal of Applied Physics, 2010
Abstract Efficient photoelectrochemical H 2 production by solar irradiation depends not only on t... more Abstract Efficient photoelectrochemical H 2 production by solar irradiation depends not only on the photocatalyst's band gap and its band-edge positions but also on the detailed electronic nature of the bands, such as the localization or delocalization of the band edges ...
International Journal of Quantum Chemistry, 2005
76019-We will present a study of oxygen molecule adsorption on a Pu (111) surface using the gener... more 76019-We will present a study of oxygen molecule adsorption on a Pu (111) surface using the generalized gradient approximation to density functional theory using the DMol3 suite of programs [1]. Horizontal approaches on center site, with and without spin polarization, were found to be the highest chemisorbed sites among all the cases studied here with chemisorption energies of 8.365eV and 7.897eV, respectively. The second highest chemisorption energy occurs at the vertical approach on bridge site with chemisorption energy of 8.294eV (non-spin-polarized) and 7.859eV (spin-polarized). In general, with spin polarization, dissociative adsorption with a layer by layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable compared to molecular adsorption. Non-spin-polarized chemisorption energies are usually higher than the spin-polarized energies. We also find that 5f electrons are more localized in spin polarized case, than the non-spin polarized counterparts. The ionic part of O-Pu bonding plays a significant role along with the Pu 5f-O 2p hybridization. [1] B.
The European Physical Journal D, 2006
Fullerene-like silicon nanostructures with twenty and twenty-four carbon atoms on the surface of ... more Fullerene-like silicon nanostructures with twenty and twenty-four carbon atoms on the surface of the Si60 cage by substitution, as well as inside the cage at various orientations have been studied within the generalized gradient approximation to density functional theory. Full geometry optimizations have been performed without any symmetry constraints using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the silicon atom, the Hay-Wadt pseudopotential with the associated basis set is used for the core electrons and the valence electrons, respectively. For the carbon atom, the Dunning/Huzinaga double zeta basis set is employed. Electronic and geometric properties of these nanostructures are presented and discussed in detail. Optimized silicon-carbon fullerene like nanostructures are found to have increased stability compared to the bare Si60 cage and the stability depends on the number and the orientation of carbon atoms, as well as on the nature of silicon-carbon and carbon-carbon bonding.
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Papers by Muhammad Rijalul Huda