scholarly journals Molecular Orbital Calculation of Lead-Free Perovskite Compounds for Efficient Use of Alkaline and Alkaline Earth Metals

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 956
Author(s):  
Naohisa Takesue ◽  
Jun-ichi Saito
Keyword(s):  
Transition Metals ◽  
Molecular Orbital ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Molecular Orbital Calculation ◽  
The Body ◽  
Alkaline Earth Metals ◽  
Lead Free ◽  
Covalent Bonds ◽  
Alkaline Earth Metal Ions

The effective ionic charges of lead-free perovskite dielectric complex compounds were investigated with molecular orbital calculation. The base model was a double perovskite cluster that consisted of octahedral oxygen cages with a transition metal ion of titanium, niobium, or zirconium located at each of their centers, and alkali and/or alkaline earth metal ions located at the body center, corners, edge centers, or face centers of the cluster. The results showed significant covalent bonds between the transition metals and the oxygens, and the alkali metals, especially sodium and oxygen. On the other hand, the alkaline earth metals have weak covalency. Calculation was also performed with the replacement of some of the oxygens with chlorine or fluorine; such replacement enhances the covalency of the transition metals. These trends provide good guidelines for the design properties of lead-free perovskite piezoelectrics based on ubiquitous sodium use.

The activities of evaporated metal films in gas chemisorption

1953 ◽  
Vol 218 (1135) ◽  
pp. 566-577 ◽  
Keyword(s):  
Transition Metals ◽  
Alkaline Earth ◽  
Metal Films ◽  
Alkaline Earth Metals ◽  
Light Metals ◽  
Covalent Bonds ◽  
Catalytic Systems ◽  
Single Exception ◽  
Electron Donation

The interaction of N 2 , H 2 , CO, C 2 H 4 , C 2 H 2 and O 2 with clean evaporated films of some twenty metals has been investigated between 0 and – 183° C. The results are expressed as gas chemisorbed or gas not chemisorbed. O 2 chemisorption is universal among all the metals studied, with the single exception of Au. Chemisorption of N 2 and H 2 is limited to transition metals and alkaline earth metals, and chemisorption of CO, C 2 H 4 and C 2 H 2 to these and to Al, Cu and Au. O 2 chemisorption is believed to take place with formation of O 2- ions at the surface, with electron donation from the s and p bands of the metals. The inactivity of Au towards O 2 is, however, only partly understandable in terms of this mechanism . The remaining five gases are believed to form covalent bonds with the metal d bands in chemisorption; with Cu and Au it is suggested that d – s promotion takes place in the act of chemisorption to allow such covalence. Al is exceptional, and with the light metals, s and p band electrons may be active in chemisorption: a further exception is the interaction of K with C 2 H 2 . Some applications of these results to catalytic systems are discussed.

scholarly journals Interactions Between Zinc Oxide and Alkali Metals, Alkaline Earth Metals and Halogens: A Theoretical Study

2017 ◽  
Vol 29 (3) ◽  
pp. 585-588
Author(s):  
Aned de Leon ◽  
Grace Jouanne-Jeraissati ◽  
Agustín Martínez-Contreras
Keyword(s):  
Zinc Oxide ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Theoretical Study ◽  
Alkaline Earth Metals

The Use of Some Ion-Exchange Sorbing Tracer Cations in Insitu Experiments in High Saline Groundwaters

1994 ◽  
Vol 353 ◽  
Author(s):  
J. Byegård ◽  
G. Skarnemark ◽  
M. Skålberg
Keyword(s):  
Ion Exchange ◽  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Exchange Capacity ◽  
Alkaline Earth Metals ◽  
Crushed Granite ◽  
The Difference

AbstractThe possibility to use alkali metals and alkaline earth metals as slightly sorbing tracers in in-situ sorption experiments in high saline groundwaters has been investigated. The cation exchange characteristics of granite and some fracture minerals (chlorite and calcite) have been studied using the proposed cations as tracers. The results show low Kd’s for Na, Ca and Sr (∽0.1 ml/g), while the sorption is higher for the more electropositive cations (Rb, Cs and Ba). A higher contribution of irreversible sorption can also be observed for the latter group of cations. For calcite the sorption of all the tracers, except Ca, is lower compared to the corresponding sorption to granite and chlorite. Differences in selectivity coefficients and cation exchange capacity are obtained when using different size fractions of crushed granite. The difference is even more pronounced when comparing crushed granite to intact granite.

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