scholarly journals Stability of Atrazine–Smectite Intercalates: Density Functional Theory and Experimental Study

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 554
Author(s):  
Daniel Moreno-Rodríguez ◽  
Ľuboš Jankovič ◽  
Eva Scholtzová ◽  
Daniel Tunega
Keyword(s):  
Density Functional Theory ◽  
Adsorption Capacity ◽  
Density Functional ◽  
Interlayer Space ◽  
Negative Impact ◽  
Experimental Methods ◽  
Functional Theory ◽  
Environment And Health ◽  
Correct Assignment ◽  
Organically Modified

Atrazine (A) is one of the most applied herbicides and has a negative impact on the environment and health. Density functional theory (DFT) and experimental methods were used in the study of the immobilization of atrazine in two smectites, montmorillonite (Mt) and beidellite (Bd), as well as in their organically modified structures. Four systems were examined: A-Mt and A-Bd, as well as the structures modified by tetramethylphosphonium cation (TMP), A-TMP-Mt and A-TMP-Bd. The calculations revealed a flat arrangement of the atrazine in the interlayer space of both smectites with higher stability of beidellite structures. The presence of the TMP cation increased the fixation of atrazine in both organically modified smectites. The calculated vibrational spectra allowed a detailed analysis of the overlapping bands observed in the experimental FTIR spectra and their correct assignment. Further, selected FTIR bands unambiguously assigned to atrazine and both smectites served for the estimation of the adsorbed amount of atrazine. It was shown that the adsorption capacity of both TMP-modified smectites did not increase in comparison to the adsorption capacity of unmodified smectite samples.

scholarly journals Study on the adsorption selection of CH$$_4$$ on CuO (110) versus (111) surfaces: a density functional theory study

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Long Lin ◽  
Linwei Yao ◽  
Shaofei Li ◽  
Zhengguang Shi ◽  
Kun Xie ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Capacity ◽  
Active Sites ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Density Functional Theory Calculations ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Strong Adsorption ◽  
Selection Of

AbstractFinding the active sites of suitable metal oxides is a key prerequisite for detecting CH$$_4$$ 4 . The purpose of the paper is to investigate the adsorption of CH$$_4$$ 4 on intrinsic and oxygen-vacancies CuO (111) and (110) surfaces using density functional theory calculations. The results show that CH$$_4$$ 4 has a strong adsorption energy of −0.370 to 0.391 eV at all site on the CuO (110) surface. The adsorption capacity of CH$$_4$$ 4 on CuO (111) surface is weak, ranging from −0.156 to −0.325 eV. In the surface containing oxygen vacancies, the adsorption capacity of CuO surface to CH$$_4$$ 4 is significantly stronger than that of intrinsic CuO surface. The results indicate that CuO (110) has strong adsorption and charge transfer capacity for CH$$_4$$ 4 , which may provide experimental guidance.

Experimental methods in chemical engineering: Density functional theory— DFT

2021 ◽  
Author(s):  
Hasan Al‐Mahayni ◽  
Xiao Wang ◽  
Jean‐Philippe Harvey ◽  
Gregory S. Patience ◽  
Ali Seifitokaldani
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Chemical Engineering ◽  
Experimental Methods ◽  
Functional Theory

A density functional theory study of the hydration of calcium ions confined in the interlayer space of montmorillonites

2014 ◽  
Vol 13 (04) ◽  
pp. 1450028 ◽  
Author(s):  
Zhaoyang Lou ◽  
Houbin Liu ◽  
Yao Zhang ◽  
Yingfeng Meng ◽  
Qun Zeng ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Interlayer Space ◽  
Negative Charge ◽  
Internal Surface ◽  
Water Molecules ◽  
Surrounding Water ◽  
Functional Theory ◽  
Internal Surfaces

The structures of Ca2+hydrates in the interlayer space of montmorillonites (MMT) were studied by periodic density functional theory (DFT) calculations under the GGA/PBE approximation. Affected by the internal surfaces, which are rich of negative charge, the Ca2+hydration exhibits different behaviors from that in gas phase. The Ca2+is located at the six-oxygen-ring (SOR) on the internal surface in dry MMT, while the incoming water molecules bind with the Ca2+, the O atoms on surface, and/or with each other. The water molecules have a tendency of forming a hydrogen bond (HB) network that connects the upper and lower surfaces. Attracted by surrounding water molecules, the Ca2+gradually moves outward with increasing number of water molecules. Moreover, the hydration energy (EH) of Ca2+is determined not only by the interaction between Ca2+and H2O , but also by that among Ca2+, H2O and the surfaces. As a result, the EHhas only small changes for additional incoming water molecules, in contrast to the great and monotonic decrease in gas phase.

scholarly journals ENERGIES AND VIBRATIONAL MODES OF SPECIES FORMED BY DEHYDROGENATION OF CH4 IN PRESENCE OF O2 OVER Cr2O3(0001)

Anales AFA ◽  
2021 ◽  
Vol 32 (3) ◽  
pp. 83-87
Author(s):  
S.N. Hernández Guiance ◽  
◽  
I.D. Coria ◽  
I.M. Irurzun ◽  
◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Experimental Methods ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Methanol Formation ◽  
Dissociative States ◽  
Dissociative State ◽  
Good Agreement

In this work we perform a theoretical study of dehydrogenation process of CH4 on O2– in both molecular and dissociative states - previously adsorbed on Cr2O3(0001). Calculations are based on Density Functional Theory (DFT). The results show the methanol formation form the adsorption of CH4 on O2 in dissociative state with a formationenergy5:14 eV. Also formaldehyde was formed by the reaction of CH2with molecular O2(Eads=6:09 eV) and dioxymethylene by the reaction of CH2with O2 previously adsorbed in dissociative state on Cr2O3(0001), withEads=8:17 eV. Finally, the vibrational modes found by DFT for each of the species were compared, which are in good agreement with those of reference bibliography. This allows us to support the values found both by technical calculations and by experimental methods.

An insight into the effects of transition metals on the thermal expansion of complex perovskite compounds: an experimental and density functional theory investigation

2018 ◽  
Vol 20 (26) ◽  
pp. 17781-17789 ◽  
Author(s):  
Xiao Wang ◽  
Ye Han ◽  
Xiaojie Song ◽  
Weihui Liu ◽  
Yinxi Jin ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Thermal Expansion ◽  
Transition Metals ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Experimental Methods ◽  
Complex Perovskite ◽  
Functional Theory ◽  
Insight Into

The doping of transition-metals can suppress the growth of the perovskite grain and decrease the TECs of the compounds. The mechanisms were studied using experimental methods and theoretical calculations.

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