Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Hemenkumar H. Thakar, Mrunalkumar D. Chaudhari, Jaykumar Vora; Importance of high strength steels and their welding in petrochemical industries. AIP Conf. Proc. 5 January 2024; 2960 (1): 030008. https://doi.org/10.1063/5.0184275 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Critical equipments of process and heavy engineering industries are prone to significant wear due to intense service conditions. Uneven and uncontrolled wear causes significant changes in dimensional and geometrical accuracies of the part surfaces, which adversely affect the parts’ functionality and service life of these parts. Shorter service life of these equipments and subsequent replacement of the same is one of the serious economic concerns. Hardfacing or hardsurfacing is comparatively an advanced metal deposition technology to deposit a hard and complex metal substrate layer on simple and softer base material surface. This process is gaining popularity at commercial level due to its unique capabilities to develop superior wear, corrosion, and impact resistance properties on worn out parts and offer huge economic advantage as substitute to costly replacement. The primarily aim of this study is to present a comprehensive review of the work done on the probable candidates for deposition materials, and summarize the influence of various process parameters on hard-faced surface characteristics. The critical issues like dilution, debonding, and residual stresses have been discussed for multi-layered hardfacing for iron-, nickel-, and cobalt-based hardfacing materials. The secondary aim of this study is to address practical issues such as selection of proper combination of base-substrate material, to understand the response characteristics of ‘plasma transferred arc hardfacing (PTAHF)’ process to minimize the de-bonding, dilution, and residual stresses and finally to improve quality of hardfacing practice.

Arc welding is a type of welding in which there is an electric arc formed joining the base material and the electrode, as well as metals are melted at the welding spot with the help of a welding power source. Arc welding is commonly used because of its low capital and operational costs. Due to cost concerns, it is typically not viable to fabricate components from solid high alloyed materials. As a result, non-alloyed or low-alloy base materials must be encased with high-alloy cladding. In high-tech welding technique processes, Strip electrodes are used to apply welded deposits over large surface areas.The most important contribution of this article is to optimize plasma arc welding process parameters for dissimilar metal welding and other quality factors such as bead shape, microstructure, hardness, ferrite measurement, and tensile test.Due to its exceptional features, low dispersion, and high coatings efficacy, Welding with plasma transmitted arc (PTAW) is a broadly applied overlay coating method. The impacts of transferred welding current, welding travel speed, powder flow rate, welding oscillation speed, and stand-off distance on weld bead form parameters such as width of deposition and reinforcing are given and examined using experimental data and a developed model. Reduced current (100–120 A), intermediate travel speed (120–140 mm/min), intermediate powder feed rate (12–14 g/min), oscillation speed (450–550 mm/min), and stand-off distance (6–8 mm) would result in superior deposition characteristics with less distortion, residual stresses, and no surface defects.

The authors in this research paper have investigated the process of hardfacing, which is a well-established manufacturing process for increasing the durability of industrial components, which are subjected to extreme wear, erosion, abrasion. The objective of this study is to establish a scientific methodology to select the most suitable combinations of materials as base-deposition materials for hardfacing, specifically focusing on Nickel-based and Cobalt-based materials. In order to make an informed decision, multi-criteria decision-making method known as “Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)” is used. This technique permits to deal with wide range of important factors, such as the materials' high-temperature resistance, wear resistance, and corrosion resistance, among others. The paper discusses a step-by-step approach to selecting the best alternative material for hardfacing by considering eight different criteria and assigning preferences to each of the available materials. The results of this methodology suggested that Stellite-6 based cobalt-based alloy is best suitable for AISI 304 grade austenitic stainless steel materials used for high temperature applications.

This study examines the utilization of metal-cored filler wire in conjunction with the gas metal arc welding (GMAW) technique for welding high-strength S690QL steel. Since welding parameters significantly impact the bead quality and weld joint integrity, the main objective was to identify the optimal welding parameters. To achieve this, the input variables including the current (A), voltage (V), and gas flow rate (GFR), and their effects were evaluated for reinforcement (R), width (W), depth of penetration (DOP), and the width of the heat-affected zone (HAZ). For a more efficient and cost-effective investigation, a Box–Behnken design, which is based on response surface methodology, was used for bead-on-plate trials. Mathematical regression models, derived from experimental data, were rigorously validated using the analysis of variance, main effects plots, residual analysis, and the R 2 and Adj. R 2 values. Additionally, the heat transfer search (HTS) algorithm was employed for process optimization. While single-objective optimization provided optimal settings for individual responses, simultaneous optimization aimed to strike a balance between multiple, sometimes conflicting, objectives. This comprehensive approach resulted in specific values, including a reinforcement (R) of 4.285 mm, a width (W) of 9.906 mm, a DOP of 2.039 mm, and an HAZ width of 2.020 mm. These values were achieved with specific input parameters: current (221 A), voltage (24 V), and GFR (21 L·min−1). The Pareto solutions offered a nuanced selection of the most suitable configuration, taking into account the desired values for R, W, DOP, and HAZ. The close alignment between predicted and experimentally measured values for the responses highlights the precision and suitability of the HTS algorithm in estimating critical bead geometries during GMAW of S690QL plates.

This article presents a comprehensive study on the application of Hastelloy C-22 powder weld overlay on SA 240 Type 316L austenitic stainless steel using the laser beam welding process. This novel combination of materials and processes was investigated for the first time, focusing on its potential utility for various industrial applications. Various testing techniques, including visual testing, hardness testing, bend testing, chemical composition analysis using optical spectroscopy, corrosion resistance assessment through the potentiodynamic polarization technique, and macro- and microstructural observation, were employed to evaluate the performance of the weld overlay. The research findings had several significant outcomes. Notably, precise control and minimal alloy mixing were achieved, as evidenced by the dilution at a remarkable height of 0.5 mm from the base metal. The laser welding process resulted in a minimal heat-affected zone and a fine columnar interdendritic microstructure, with average primary and secondary arm spacing values of 3.981 µm and 2.289 µm, respectively. Rigorous visual and bend testing confirmed the integrity of the sound welds in the overlay. Moreover, the high-quality finish of the weld overlay eliminated the need for extensive machining and finishing processes, resulting in cost reductions. This study also demonstrated primary and secondary inter-laminar spacing, leading to improved overall structural integrity. Additionally, the weld overlay exhibited excellent hardness characteristics. The current work contributes to the advancement of welding processes and provides practical solutions to enhance efficiency, cost-effectiveness, and structural performance in relevant industrial applications.

Nickel-based hardfacing alloys are widely used for the prevention of corrosion and wear losses in various industrial applications. They are prepared by various processes, and their properties are dependent on process parameters. In this study, the ERNiCr-B hardfacing alloy was deposited on AISI 304 stainless steel substrate using gas tungsten arc welding (GTAW) process using various processing parameters. Process parameters, namely, current, pre-heating temperature, and shielding gas flow rate of the GTAW process were optimized via Taguchi method. Confirmation test proved the validity of the optimization method. The optimum values of current, pre-heating temperature, and gas flow rate of the GTAW process for the deposition of ERNiCr-B hardfacing alloy on the 304 stainless steel substrate with respect to bead reinforcement were 130 A, 303.15 K, and 0.00015 m 3 /s, respectively. At optimum deposition condition, no evidence of defects such as microcracks, porosity, inclusions, etc. were observed in the hardfaced alloy. Among various parameters, the current had the most significant effect on dependent variables such as bead width, reinforcement height, hardness, and corrosion resistance of hardfaced deposit. Microstructural examination showed a typical dendritic structure with eutectic phases distributed in the inter-dendritic regions. Furthermore, the energy-dispersive X-ray spectroscopic (EDS) analysis showed the evidence of Fe dilution in ERNiCr-B deposit away from the substrate, which showed profound effect on hardness, microstructure, and corrosion rate.

Hastelloy – C series weld overlay is an area of great significance in the present chemical processing industries, pressure vessel, and heat exchanger industries. Hastelloy – C series of alloys has been one of the least studied and understood classes of materials. The purpose of this studied is to understand and compare the performance of Hastelloy – C series nickel–chromium–molybdenum alloys with the view of metallurgical, mechanical, and physical properties, corrosion resistance, and weld overlay aspects. Characteristics of various nickel and nickel-based alloys with a focus on the Hastelloy – C series have been presented through a comparison of physical and mechanical properties, applications, and corrosion behavior in different atmospheres. A comprehensive review has been done to study the effect of alloying element addition on phase stability, the formation of topological-closed-packed phase (TCP), transformation sequence of Hastelloy C-4, C-276, and C-22. The importance of dilution for weld overlay, selection of welding process, selection of filler wire, recommended joint geometry, and weld sequencing for Hastelloy – C series weld overlay has been discussed in detail. This review will help to understand the effect of high Mo with Fe and W on the formation of TCP phases, the corrosion behavior of C-2000 in an oxidizing and reducing atmosphere, and the role of dilution in weld overlay from conventional and advanced conventional welding process point of view.

Background Supra-Ventricular Tachycardia (SVT) is the commonest pathological tachycardia in newborns. West Midlands hospitals generally rely on the Advanced Paediatric Life Support (APLS) guideline to manage Neonatal SVT. This guideline is not neonate specific and Neonatal advanced nurse practitioners are not APLS trained. Aim On behalf of the West Midlands Children’s Cardiac Network, we designed a survey to explore local practices, understand the dilemmas faced with neonatal SVT, as well as to determine the acceptability of a neonatal SVT guideline. Methods An online questionnaire was designed using a survey programme, incorporating 10 questions on aspects of neonatal SVT and local practices, and this was sent out via email to all paediatric and neonatal consultants in the region and results collated using the survey software. Results There were 43 responses, of which 74% were paediatricians, 19% neonatologists and the remainder PEC’s. Responses covered 80% of regional trusts. 67% used the APLS guideline to manage neonatal SVT, with 3% using a local guideline. However 30% discussed management directly with a paediatric cardiologist. Of those that used the APLS guideline, 36% did this because the baby was haemodynamically compromised. For non-haemodynamically compromised SVT, 84% said they would use vagal manoeuvres as first-line management. If vagal manoeuvres and IV Adenosine failed, 93% of responders would contact a paediatric cardiologist as their next management step. A free-text question on the most difficult decision making dilemmas when faced with neonatal SVT had common comments of what chemical cardioversion could be used if adenosine failed, timing for DC Cardioversion, and when to transfer to regional centre. In terms of acceptability of a regional guideline, 70% said they would be happy to use this. An additional question on out-of-hours availability of ECG machines, showed that 10% of responders had no access to this. Conclusion The majority of responders indicated that they would happy to use a regional guideline and so we have used the results of this survey to inform this guideline, including guidance for the common dilemmas faced, with clear flowcharts, as well as appendices on the common drugs used. Finally, we would suggest that this guideline could be applicable nationally, via the PECSIG group.

Nickel-based superalloys are critical for aerospace and power applications due to excellent high-temperature properties. These high-temperature properties are attributed to the coherently precipitated gamma prime phase in the gamma matrix. The segregation of alloying elements between the matrix and the gamma prime phase drives precipitate misfit strains and impacts material strength. This study aims at understanding the site preference of Co and Cr within the ordered gamma prime phase. The study also calculates the interaction energy between alloying additions within the ternary systems Ni-Al-Cr and Ni-Al-Co, and the quaternary system Ni-Al-Cr-Co. It is found that Co has mixed substitution behavior between the Al and Ni sites in the gamma prime phase. The results from the Ni-Al-Cr ternary system show that two Cr atoms prefer being close to each other, with the most stable configuration of the first nearest neighbors of the Al-Al site. The interaction energies calculated from the Ni-Al-Co system show that the initial distance between two Co atoms will decide whether the two Co atoms prefer Ni-Ni or Ni-Al configuration. The study on the quaternary system Ni-Al-Cr-Co reveals that the initial configuration of Cr and Co atoms will affect the final most stable configuration. The results are found to be consistent with our previous findings.

Transition-metal dopants play a critical role in the high-temperature mechanical strength and corrosion resistance of nickel-based superalloys. In this article, the site occupancy behavior of chromium in gamma'-Ni3Al has been investigated by combining three-dimensional (3D) atom probe and high-resolution transmission electron microscopy characterizations with ab initio density functional theory (DFT) calculations. The 3D atom probe data show a clear preference of chromium on the aluminum sublattice over the nickel sublattice in Rene88 super alloys. First-principles DFT total-energy calculations were performed to understand the site occupancy of chromium in the L1(2) structured gamma-Ni3Al. The obtained chromium site preference energies have been compared using the anti-site and vacancy-based substitution formation mechanism, as well as using the standard defect formation formalism. It was found that chromium prefers aluminum site, consistent with the 3D atom probe result. In addition, interaction energies between two chromium atoms have also been determined from first-principles calculations. Our results show that chromium atoms prefer to be close by on either nickel or aluminum sublattices or on a nickel-aluminum mixed lattice, suggesting a potential tendency of chromium segregation in the gamma' phase.

Integration of low dielectric constant (k) materials such as organosilicate glasses (OSG) into microelectronic processing demands a better of understanding the plasma/OSG interactions during plasma etching and ashing of these materials, based on which low-k materials with higher radiation resistance and better mechanical behaviors can be developed and optimized plasma processing conditions can be introduced to ensure continued miniaturization of semiconductor devices. Introducing organic crosslinking (e.g., –CH2–) in OSG has been shown to be an effective measure to improve the mechanical properties but their effect on plasma interaction is still not fully understood. In this paper, ab initio based molecular dynamics simulations have been employed to investigate the effect of the oxygen plasma on the carbon-bridged silicate networks in the OSG material. The results show that organic crosslinking in the Si–O–Si network leads to lower energy reaction pathways with atomic oxygen radicals that result in breakage of Si–CH2–Si linkages instead of Si–CH3 bonds and, consequently, a decrease in carbon removal. The incorporation of organic crosslinking groups can thus improve the resistance to oxygen plasma damage of OSG and, together with better mechanical properties, can lead to the design of stronger low-k dielectric films.

Nickel based superalloys have superior high temperature mechanical strength, corrosion and creep resistance in harsh environments and found applications in the hot sections as turbine blades and turbine discs in jet engines and gas generator turbines in the aerospace and energy industries. The efficiency of these turbine engines depends on the turbine inlet temperature, which is determined by the high temperature strength and behavior of these superalloys. The microstructure of nickel based superalloys usually contains coherently precipitated gamma prime (?) Ni3Al phase within the random solid solution of the gamma () matrix, with the ? phase being the strengthening phase of the superalloys. How the alloying elements partition into the and ? phases and especially in the site occupancy behaviors in the strengthening ? phases play a critical role in their high temperature mechanical behaviors. The goal of this dissertation is to study the site substitution behavior of the major alloying elements including Cr, Co and Ti through first principles based calculations. Site substitution energies have been calculated using the anti-site formation, the standard defect formation formalism, and the vacancy formation based formalism. Elements such as Cr and Ti were found to show strong preference for Al sublattice, whereas Co was found to have a compositionally dependent site preference. In addition, the interaction energies between Cr-Cr, Co-Co, Ti-Ti and Cr-Co atoms have also been determined. Along with the charge transfer, chemical bonding and alloy chemistry associated with the substitutions has been investigated by examining the charge density distributions and electronic density of states to explain the chemical nature of the site substitution. Results show that Cr and Co atoms prefer to be close by on either Al sublattice or on a Ni-Al mixed lattice, suggesting a potential tendency of Cr and Co segregation in the ? phase.

Nickel based super alloys are used in turbine engines for aerospace and land based applications. These alloys have unique combinations of high temperatur e tensile strength, creep and oxidation resistance. The precipitation of Ll(2) structured Ni3Al gamma prime phase in the gamma matrix is one of the major strengthening mechanism of these alloys. Various studies have shown that the high temperatur e creep and oxidation resistance of the nickel based alloys can be improved by the addition of substitutional elements. The distribution of these elements in the gamma and gamma prime phases and their site occupancy behavior in gamma prime precipitate (Ni3Al) are especially important to the high temperatur e properties. In this paper, we investigated site occupancy of a common substitutional element, chromium in the gamma'-Ni3Al using periodic Density Functional Theory (DFT) based first principles calculations. Comparisons are made between the site occupancy behavior using formalism namely vacancy based, anti-site based and standard defect formation based formalism. The impact of the simulation size (2x2x2 and 3x3x3) has also been studied in order to gain more understanding of the simulation size effect on the occupancy behavior. In addition, this paper also investigated the interaction energy between two substituted atoms as a function of separation distance has also been studied. Various comparisons are made between our results, existing theoretical and experimental studies in the literature.

The mechanical properties of Ni-base superalloys are strongly influenced by ordered γ'-Ni3Al precipitates, whose growth and coarsening are controlled by the site occupancy of elements within the structures. The site occupancy behavior of Cr in γ'-Ni3Al is investigated by ab initio based Density Functional Theory based computational studies and 3D atom probe tomography. Three formalisms related to site occupancy are discussed, including standard defect formation formalism, antisite based formalism, and vacancy based formalism. The calculated substitutional energies of the Cr atom at the Ni and Al sublattice sites indicate that Cr has a strong preference for the Al site. Comparisons between the formalisms indicate that standard defect formation formalism gives an inconsistent result and vacancy based mechanism will dominate in the substitution process. The effect of additional Cr atoms calculated by the interaction energies of two Cr atoms suggests that Cr atoms prefer to be on nearest neighbor lattice sites: either in the Al, Ni, or mixed sublattice sites. Composition profiles calculated through atom probe tomography were used for analyzing the site occupancy of different elements. Based on the composition profiles for Cr, Ti and Al, it can be seen that Cr occupies the Al sublattice site in the complex Rene-88 alloy and clearly agrees with the computational results. Ni-base superalloys find major applications in the hot sections of aerospace engines, industrial gas turbines and marine turbines where their creep, oxidation, and strength properties make them ideal materials. The high temperature mechanical behavior of the superalloys is critical to increase the engine operating temperature and improve fuel efficiency while maintaining power generation requirements. The structure of most precipitation strengthened Ni-base superalloys consists of a gamma matrix (γ) with precipitates (γ’). The γ-phase is a solid solution with a face-centered crystal (fcc) lattice and randomly distributed different species of atoms. The primary strengthening phase in Ni-based superalloys is Ni3(Al,Ti), and is called gamma prime (γ'). It is a coherently precipitating phase with an ordered L12 (fcc) crystal structure. The high temperature strength, creep and corrosion resistance can be improved by introducing alloying elements such as Cr, Co and other elements. Partitioning of these alloying elements into the γ matrix and the γ’ phase plays a critical role in the strengthening mechanisms of these super alloys. A number of studies have investigated the partitioning of transition metal elements (such as Cr, Co, W, and Ta) using both experimental and computational methods. Previous atom-probe tomography (APT), scanning electron microscopy (SEM), atom location by channeling enhanced microanalysis (ALCHEMI) technique, and other techniques have concluded that Cr occupies the Al sublattice in γ'. Atom probe field ion microscopy (APFIM) has been used by several researchers to measure the site preference of atoms like Co in Ni3Al. Additionally, several computational techniques have been used in the literature including first ab initio based, first principles method, EAM potential based, cluster variation methods to calculate the site preference for different alloying additions in Ni3Al. A lot of earlier theoretical work to predict the site preference was based on the standard defect formalism which involved calculating the difference in formation enthalpies of two alloys, each containing one defect atom on the Ni and Al sublattice site respectively. In this approach, the energy depends on the choice of the reference state and is therefore not complete. Another approach used by 1 Approved for public release; distribution unlimited. Jiang et al 7 used the antisites as mediators for site substitution. In this paper, we present our results of a systematic comparison of characterizing the site preference of the above mentioned formalisms and a vacancy based formalism for Cr, which is the most common alloying elements Ni3Al. The computational results are compared to 3D atom probe experimental methods. In addition, the effects of two Cr atoms in the Ni-Ni, Al-Al and Ni-Al sublattice sites as a function of separation distance are also investigated. All the calculations were done using the plane-wave pseudopotential method as implemented in Vienna ab initio Simulation Package (VASP). A plane wave basis set with a kinetic energy cutoff of 400 eV and the Projected Augmented Wave (PAW) potentials were used in the calculations. The generalized gradient approximation (GGA) with the PBE form was used for the exchange and correlation functions. All of the calculations performed were spin-polarized. The atomic structure was fully relaxed until the forces acting on each of the atoms were less than 0.01 eV/Å. A 2x2x2 and 3x3x3 periodic supercell was employed for defect calculations. A 3x3x3 supercell was required to calculate the interaction between two Cr atoms. A k-mesh size of 9x9x9 and 4x4x4 was used for the two supercells respectively. The lattice parameter was calculated to be 3.567 Angstroms in good agreement with previous reports. The formation energies of intrinsic defects was first determined in Ni3Al using the standard defect formation formalism. These included vacancies i.e., VaNi and VaAl, and anti-sites i.e., NiAl and AlNi. The total defects involved thermal defect complexes also, including exchange-type (0  AlNi + NiAl ) and Schottky-type (0  3VaNi + VaAl) defects. The formation energies for the intrinsic defects are calculated in both the supercell sizes. The results are listed in Table 1, and are in good agreement with the existing results of DFT calculations, experimental studies and those calculated from EAM potentials. The total energies of (Ni,Cr)3Al and Ni3(Cr,Al) alloy structures were calculated by substituting one Cr atom at the Ni or the Al sites. Three different formalisms were employed to characterize the sitepreference behavior of Cr in γ’, including the standard defect formalism, antisite based formalism, and the vacancy based formalism. Although the former two have been widely used in the literature to determine site preferences, the vacancy based mechanism has not been. In the standard defect formalism, the substitutional formation energies are calculated as per the definition below: The configuration with the lowest formation energy is the preferred sublattice for the alloying atom. This approach is not complete since the energies depend on the choice of reference states for the pure elements. The elemental chemical potentials of Ni, Al and Cr were found out to be -5.748, -3.733 and 9.594 eV atom respectively. The energies calculated using the equation above in both the 32-atom and 108-atom supercell indicate that Cr prefers the Ni-sublattice, in agreement with Jiang et al and in disagreement with Seidman. The anti-site based substitutional formalism has been adopted by several researchers from Ruban and Skriver to Chao Jiang. In this formalism, the mediator for the site substitution is anti-sites. The parameter Al Ni Cr E → is defined as the energy required in moving an atom from one sublattice site to the other sublattice site via the reaction so that the absolute value of the parameter is totally independent of the elemental reference states or its chemical activities. The energy required in transferring a Cr atom from a Ni sublattice site to an Al sublattice site was calculated using the following equation:

The interactions of the oxidizing plasma with the low k dielectric materials and the associated damage mechanisms are of great technological interest for processing current and next generation low k materials. Density functional theory based ab initio molecular dynamics simulations have been performed to evaluate the reaction mechanisms of thermal atomic oxygen [in triplet (P3) or singlet (D1) state] with the organosilicate low k materials represented by model systems. The threshold kinetic energies of attacking atomic oxygen and the reaction pathway were found to be highly incident angle dependent. Carbon abstraction through methyl radical formation can happen at energy barriers as low as 0.1 eV when O radical attack occurs along the axes inclined to the Si–C bond. The simulation results agree well with recent experiments and support diffusion-controlled etching rate dependence, and dielectric constant increases due to oxygen plasma etching.

Submitted for the MAR11 Meeting of The American Physical Society Ab initio study of the thermodynamic properties and the phonon calculations of Zircon and Reidite MRUNALKUMAR CHAUDHARI, JINCHENG DU, University of North texas — Zircon and Reidite are the polymorphs of Zirconium Silicate which find its importance geologically, because of its natural hosting to various radioactive elements in the crust of the earth. High permittivity also makes it a promising material for the gate dielectric material in metal-oxide semiconductors. Knowledge of the thermodynamic properties and the phonon based calculations is very critical to understand the high temperature and high pressure properties in order to consider its application as an effective natural storage for the radioactive wastes. These properties are thoroughly studied both computationally and experimentally for zircon, while significantly less attention was paid to reidite in the literature. The thermodynamic properties and phonon calculations of Zircon and Reidite were studied using ab initio based periodic density-functional theory (DFT) based calculations using the generalized gradient approximation (GGA). Various properties such as free energy, internal energy, entropy, heat capacity and thermal displacement as a function of temperature is calculated using the PHONON software. Various phonon based density of states and dispersion curves are calculated and compared with the experimental data. No first principles based computational results were reported up to now. Calculated bulk properties agree very well with the experimental data in the literature. Mrunalkumar Chaudhari University of North Texas Date submitted: 19 Nov 2010 Electronic form version 1.4