scholarly journals Defects and Calcium Diffusion in Wollastonite

Chemistry ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 937-946
Author(s):  
Sumudu Nimasha ◽  
Sashikesh Ganeshalingam ◽  
Navaratnarajah Kuganathan ◽  
Konstantinos Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Activation Energy ◽  
Defect Cluster ◽  
Slow Diffusion ◽  
Pair Potentials ◽  
Simulation Based ◽  
Calcium Diffusion ◽  
Engineering Strategy ◽  
Ca Ions ◽  
Defect Process

Wollastonite (CaSiO3) is an important mineral that is widely used in ceramics and polymer industries. Defect energetics, diffusion of Ca ions and a solution of dopants are studied using atomistic-scale simulation based on the classical pair potentials. The energetically favourable defect process is calculated to be the Ca-Si anti-site defect cluster in which both Ca and Si swap their atomic positions simultaneously. It is calculated that the Ca ion migrates in the ab plane with an activation energy of 1.59 eV, inferring its slow diffusion. Favourable isovalent dopants on the Ca and Si sites are Sr2+ and Ge4+, respectively. Subvalent doping by Al on the Si site is a favourable process to incorporate additional Ca in the form of interstitials in CaSiO3. This engineering strategy would increase the capacity of this material.

scholarly journals Simulation-Based Defect Engineering in “α-Spodumene”

2021 ◽  
Vol 5 (3) ◽  
pp. 57
Author(s):  
Sivanujan Suthaharan ◽  
Poobalasuntharam Iyngaran ◽  
Navaratnarajah Kuganathan
Keyword(s):  
Density Functional ◽  
Lithium Ion ◽  
Defect Cluster ◽  
Intrinsic Defect ◽  
Ion Diffusion ◽  
Defect Engineering ◽  
Functional Theory ◽  
Pair Potentials ◽  
Simulation Based ◽  
Defect Process

Naturally occurring lithium-rich α-spodumene (α-LiAlSi2O6) is a technologically important mineral that has attracted considerable attention in ceramics, polymer industries, and rechargeable lithium ion batteries (LIBs). The defect chemistry and dopant properties of this material are studied using a well-established atomistic simulation technique based on classical pair-potentials. The most favorable intrinsic defect process is the Al-Si anti-site defect cluster (1.08 eV/defect). The second most favorable defect process is the Li-Al anti-site defect cluster (1.17 eV/defect). The Li-Frenkel is higher in energy by 0.33 eV than the Al-Si anti-site defect cluster. This process would ensure the formation of Li vacancies required for the Li diffusion via the vacancy-assisted mechanism. The Li-ion diffusion in this material is slow, with an activation energy of 2.62 eV. The most promising isovalent dopants on the Li, Al, and Si sites are found to be Na, Ga, and Ge, respectively. The formation of both Li interstitials and oxygen vacancies can be facilitated by doping of Ga on the Si site. The incorporation of lithium is studied using density functional theory simulations and the electronic structures of resultant complexes are discussed.

scholarly journals Structural and Defect Properties of LiTi2(PO4)3

2021 ◽  
Vol 11 (5) ◽  
pp. 13268-13275
Keyword(s):  
Atomistic Simulation ◽  
Three Dimensional ◽  
Intrinsic Defect ◽  
Ion Diffusion ◽  
Ion Migration ◽  
Pair Potentials ◽  
Simulation Based ◽  
Engineering Strategy ◽  
Li Ion ◽  
High Chemical Stability

LiTi2(PO4)3 is an attractive electrolyte material in Li-ion batteries' application due to its high ionic conductivity and high chemical stability. Here we employ atomistic simulation based on the classical pair potentials to examine the intrinsic defect processes, Li-ion migration, and solution of various dopants in LiTi2(PO4)3. The Li-Frenkel (0.73 eV) is calculated to be the most favorable defect energy process ensuring the formation of Li vacancies required for the vacancy-assisted Li-ion migration. Long-range three-dimensional lithium vacancy migration was observed with a low activation energy of 0.36 eV, inferring fast Li-ion diffusion. The most favorable isovalent dopants on the Li and Ti sites are Na and Si, respectively. Li interstitials' formation in these materials is favored by doping of Ga on the Ti site. This engineering strategy can be of interest to improve the capacity of LiTi2(PO4)3.

scholarly journals Calcium Diffusion in a Mugearite Melt

1973 ◽  
Vol 10 (3) ◽  
pp. 394-402 ◽  
Author(s):  
G. A. Medford
Keyword(s):  
Activation Energy ◽  
Electron Microprobe ◽  
Diffusion Rate ◽  
Temperature Range ◽  
Calcium Diffusion ◽  
Diffusion Curves

The diffusion rate of calcium in a mugearite melt is determined to vary between 1.07 × 10−7 and 3.36 × 10−7 cm2/s for a temperature range of 1230 to 1423 °C. The activation energy of the process is 29.5 kcal per mole. Diffusion curves are measured with an electron microprobe.

Activation Energy of Formation for CaO · Al2O3and Energy for Diffusion of Ca-ions

1977 ◽  
Vol 106 (3-6) ◽  
pp. 323-325 ◽  
Author(s):  
Suketoshi Ito ◽  
Akihiro Nagai ◽  
Kazutaka Suzuki ◽  
Michio Inagaki
Keyword(s):  
Activation Energy ◽  
Ca Ions ◽  
Energy Of Formation

A simulation-based semiconductor chip yield model incorporating a new defect cluster index

1999 ◽  
Vol 39 (4) ◽  
pp. 451-456 ◽  
Author(s):  
Chi-Hyuck Jun ◽  
Yushin Hong ◽  
Soo Young Kim ◽  
Kwang-Su Park ◽  
Hangyeob Park
Keyword(s):  
Defect Cluster ◽  
Yield Model ◽  
Semiconductor Chip ◽  
Cluster Index ◽  
Simulation Based

Ultrastructural Aspects of Golgi Complex Function in Parathyroid Cells of Winter Frogs

1973 ◽  
Vol 31 ◽  
pp. 680-681
Author(s):  
William J. Dougherty
Keyword(s):  
Golgi Complex ◽  
Secretory Granules ◽  
Complex Function ◽  
Secretory Activity ◽  
Secretory Proteins ◽  
Perivascular Spaces ◽  
Pituitary Cells ◽  
Electron Microscopic ◽  
Ca Ions ◽  
Regulation Of Secretion

The regulation of secretion in exocrine and endocrine cells has long been of interest. Electron microscopic and other studies have demonstrated that secretory proteins synthesized on ribosomes are transported by the rough ER to the Golgi complex where they are concentrated into secretory granules. During active secretion, secretory granules fuse with the cell membrane, liberating and discharging their contents into the perivascular spaces. When secretory activity is suppressed in anterior pituitary cells, undischarged secretory granules may be degraded by lysosomes. In the parathyroid gland, evidence indicates that the level of blood Ca ions regulates both the production and release of parathormone. Thus, when serum Ca is low, synthesis and release of parathormone are both stimulated; when serum Ca is elevated, these processes are inhibited.

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