Pub Date : 2023-07-12DOI: 10.3390/magnetochemistry9070182
José F. Malta, M. Henriques, J. A. Paixão, A. P. Gonçalves
GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). In this work, we have obtained pure GaMo4Se8 in polycrystalline form through an innovative two-step synthetic route. Phase purity and chemical composition were confirmed through the Rietveld refinement of the powder XRD pattern, the sample characterisation having been complemented with SEM analysis. The magnetic phase diagram was investigated using DC (VSM) and AC magnetometry, which disclosed the presence of cycloidal, skyrmionic and ferromagnetic phases in polycrystalline GaMo4Se8.
{"title":"Synthesis and Structural and Magnetic Properties of Polycrystalline GaMo4Se8","authors":"José F. Malta, M. Henriques, J. A. Paixão, A. P. Gonçalves","doi":"10.3390/magnetochemistry9070182","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070182","url":null,"abstract":"GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). In this work, we have obtained pure GaMo4Se8 in polycrystalline form through an innovative two-step synthetic route. Phase purity and chemical composition were confirmed through the Rietveld refinement of the powder XRD pattern, the sample characterisation having been complemented with SEM analysis. The magnetic phase diagram was investigated using DC (VSM) and AC magnetometry, which disclosed the presence of cycloidal, skyrmionic and ferromagnetic phases in polycrystalline GaMo4Se8.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46575085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-11DOI: 10.3390/magnetochemistry9070180
Hiroyuki Tajima, Takeshi Oda, Tomofumi Kadoya
This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors is that the (organic) semiconductor/metal contacts in the MIOM capacitors are of the Schottky type, whereas the contacts in the MIS capacitors are of the ohmic type. Moreover, the mobilities of most organic semiconductors are significantly lower than those of inorganic semiconductors. As the MIOM structure is identical to the electrode portion of an organic field-effect transistor (OFET) with top-contact and bottom-gate electrodes, the hysteretic behavior of the OFET transfer characteristics can be deduced from the NTE phenomenon observed in MIOM capacitors.
{"title":"Nonthermal Equilibrium Process of Charge Carrier Extraction in Metal/Insulator/Organic Semiconductor/Metal (MIOM) Junction","authors":"Hiroyuki Tajima, Takeshi Oda, Tomofumi Kadoya","doi":"10.3390/magnetochemistry9070180","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070180","url":null,"abstract":"This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors is that the (organic) semiconductor/metal contacts in the MIOM capacitors are of the Schottky type, whereas the contacts in the MIS capacitors are of the ohmic type. Moreover, the mobilities of most organic semiconductors are significantly lower than those of inorganic semiconductors. As the MIOM structure is identical to the electrode portion of an organic field-effect transistor (OFET) with top-contact and bottom-gate electrodes, the hysteretic behavior of the OFET transfer characteristics can be deduced from the NTE phenomenon observed in MIOM capacitors.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44419561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-11DOI: 10.3390/magnetochemistry9070181
Xiaogang Yu, Renpeng Yang, Chengwei Wu, Boqi Liu, W. Zhang
Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were synthesized using a hydrothermal technique. The obtained magnetic nanoparticles (MNPs) exhibited a spinel structure, where the lattice constant decreased with the Cr3+ ion content. The doping of Cr3+ ion (x = 0.1) increased the specific saturation magnetization to 46.4 emu/g but decreased to 20.0 emu/g with the further increase in the Cr3+ ion content to x = 0.4. The decrement in Curie temperature was ascribed to the weakened super-exchange interaction between the metal ions located at A-sites and B-sites, which arose from the doping of the Cr3+ ion. The T2-weighted images gradually darkened with the increase in Zn0.6Mg0.4Cr0.1Fe1.9O4 nanoparticles concentration, suggesting that the nanoparticles can enhance the image contrast. Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were able to heat the agar phantom to the hyperthermia temperature under the safe alternating magnetic field, which showed their potential in the magnetic induction hyperthermia.
{"title":"Effect of Cr3+ Doping on Magnetic Properties of Zn-Mg Ferrite Nanoparticles","authors":"Xiaogang Yu, Renpeng Yang, Chengwei Wu, Boqi Liu, W. Zhang","doi":"10.3390/magnetochemistry9070181","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070181","url":null,"abstract":"Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were synthesized using a hydrothermal technique. The obtained magnetic nanoparticles (MNPs) exhibited a spinel structure, where the lattice constant decreased with the Cr3+ ion content. The doping of Cr3+ ion (x = 0.1) increased the specific saturation magnetization to 46.4 emu/g but decreased to 20.0 emu/g with the further increase in the Cr3+ ion content to x = 0.4. The decrement in Curie temperature was ascribed to the weakened super-exchange interaction between the metal ions located at A-sites and B-sites, which arose from the doping of the Cr3+ ion. The T2-weighted images gradually darkened with the increase in Zn0.6Mg0.4Cr0.1Fe1.9O4 nanoparticles concentration, suggesting that the nanoparticles can enhance the image contrast. Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were able to heat the agar phantom to the hyperthermia temperature under the safe alternating magnetic field, which showed their potential in the magnetic induction hyperthermia.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48397865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.3390/magnetochemistry9070179
C. Favieres
The Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects aims to provide researchers with an overview of some aspects of the current research in magnetic materials from theoretical studies to their applications, including their fabrication and characterization [...]
{"title":"Special Issue: Soft and Hard Magnetic Materials: Latest Advances and Prospects","authors":"C. Favieres","doi":"10.3390/magnetochemistry9070179","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070179","url":null,"abstract":"The Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects aims to provide researchers with an overview of some aspects of the current research in magnetic materials from theoretical studies to their applications, including their fabrication and characterization [...]","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48992239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-09DOI: 10.3390/magnetochemistry9070177
E. Fomenko, G. Akimochkina, Y. Knyazev, S. V. Semenov, V. Yumashev, L. Solovyov, A. Anshits
The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM10. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye’elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM10 to minimize solid waste pollution.
{"title":"Characterization and Magnetic Properties of Sintered Glass-Ceramics from Dispersed Fly Ash Microspheres","authors":"E. Fomenko, G. Akimochkina, Y. Knyazev, S. V. Semenov, V. Yumashev, L. Solovyov, A. Anshits","doi":"10.3390/magnetochemistry9070177","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070177","url":null,"abstract":"The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM10. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye’elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM10 to minimize solid waste pollution.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43129029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-09DOI: 10.3390/magnetochemistry9070178
Chengfang Shi, Laiwei Gao, M. Baumgarten, Dongdong Wei, Zhipeng Xu, Wenping Wang, Di Wang
In contrast to diradical linked by π-conjugation, there have been only a limited number of studies reported for those linked by homoconjugation systems. Bis(nitronyl nitroxide) diradicals and monoradical connected by a core non-rigid triptycene unit were synthesized. EPR spectroscopy and SQUID were employed to investigate the magnetic exchange interactions. The results demonstrate that the values of ΔEST are 0.19 kcal/mol (J = 34.4 cm−1) for 2,6-TP-NN and −0.21 kcal/mol (J = −36.9 cm−1) for 2,7-TP-NN, indicating ferromagnetic interaction and antiferromagnetic interaction, respectively. The spin polarization rule is not a precise predictor of the behavior of triptycene diradicals, and therefore, we improve the model. The experimental findings indicate that homoconjugation can function directly as a coupling pathway between the two spin centers, which is in qualitative agreement with the DFT theoretical calculations and the Borden rule. This research has found a special means of achieving spin coupling in non-rigid aromatics by means of homoconjugation.
{"title":"Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals","authors":"Chengfang Shi, Laiwei Gao, M. Baumgarten, Dongdong Wei, Zhipeng Xu, Wenping Wang, Di Wang","doi":"10.3390/magnetochemistry9070178","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070178","url":null,"abstract":"In contrast to diradical linked by π-conjugation, there have been only a limited number of studies reported for those linked by homoconjugation systems. Bis(nitronyl nitroxide) diradicals and monoradical connected by a core non-rigid triptycene unit were synthesized. EPR spectroscopy and SQUID were employed to investigate the magnetic exchange interactions. The results demonstrate that the values of ΔEST are 0.19 kcal/mol (J = 34.4 cm−1) for 2,6-TP-NN and −0.21 kcal/mol (J = −36.9 cm−1) for 2,7-TP-NN, indicating ferromagnetic interaction and antiferromagnetic interaction, respectively. The spin polarization rule is not a precise predictor of the behavior of triptycene diradicals, and therefore, we improve the model. The experimental findings indicate that homoconjugation can function directly as a coupling pathway between the two spin centers, which is in qualitative agreement with the DFT theoretical calculations and the Borden rule. This research has found a special means of achieving spin coupling in non-rigid aromatics by means of homoconjugation.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44663096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-08DOI: 10.3390/magnetochemistry9070176
V. Gornakov, I. Shashkov, O. Tikhomirov, Y. Kabanov
Domain wall mobility as a function of nonmagnetic interlayer thickness and temperature was studied in ultrathin exchange-coupled ferromagnetic layers using magneto-optic Kerr microscopy. The system under study is a Pt/Co/Pt/Co/Pt heterostructure having perpendicular magnetic anisotropy and a middle Pt layer with spatially variable thickness. The ferromagnetic interaction between the Co layers is observed when the Pt interlayer thickness varies from 5 to 6 nm in a temperature range of 200–300 K. There is a certain interval of Pt layer thickness where domain walls in both ferromagnetic layers move independently. Nonlinear dependence of the domain wall displacement on the applied field was measured. It is shown that an equilibrium position of the relaxed domain wall depends on field, temperature, and the nonmagnetic interlayer thickness. This position is determined by the energy balance: (i) domain wall displacement provided by the applied field, (ii) interlayer exchange interaction in the area swept by the domain wall, and (iii) domain wall coercivity. The mechanism of domain wall stabilization in terms of independent wall motion near critical thickness was considered. It is found that both the coercivity of the Co layer and the critical thickness decrease at higher temperature, while the interlayer exchange constant J is changed weakly.
{"title":"Spacer Thickness and Temperature Dependences of the Interlayer Exchange Coupling in a Co/Pt/Co Three-Layer Structure","authors":"V. Gornakov, I. Shashkov, O. Tikhomirov, Y. Kabanov","doi":"10.3390/magnetochemistry9070176","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070176","url":null,"abstract":"Domain wall mobility as a function of nonmagnetic interlayer thickness and temperature was studied in ultrathin exchange-coupled ferromagnetic layers using magneto-optic Kerr microscopy. The system under study is a Pt/Co/Pt/Co/Pt heterostructure having perpendicular magnetic anisotropy and a middle Pt layer with spatially variable thickness. The ferromagnetic interaction between the Co layers is observed when the Pt interlayer thickness varies from 5 to 6 nm in a temperature range of 200–300 K. There is a certain interval of Pt layer thickness where domain walls in both ferromagnetic layers move independently. Nonlinear dependence of the domain wall displacement on the applied field was measured. It is shown that an equilibrium position of the relaxed domain wall depends on field, temperature, and the nonmagnetic interlayer thickness. This position is determined by the energy balance: (i) domain wall displacement provided by the applied field, (ii) interlayer exchange interaction in the area swept by the domain wall, and (iii) domain wall coercivity. The mechanism of domain wall stabilization in terms of independent wall motion near critical thickness was considered. It is found that both the coercivity of the Co layer and the critical thickness decrease at higher temperature, while the interlayer exchange constant J is changed weakly.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46160557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-06DOI: 10.3390/magnetochemistry9070175
C. Cruz, N. Audebrand, D. Páez‐Hernández, V. Paredes-García
A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat cationic structure [Cu3(HL′)2(H2O)2]4+ with a Cu3 linear core reached by the double Cu-OR/NN-Cu triazole/alkoxo bridge of the hemiaminal molecule. The CuII spin carriers are antiferromagnetically coupled, presenting a spin doublet ground state (S = 1/2) with a magnetic coupling constant of −179 cm−1. Moreover, DTF calculations show that the planarity of the compound permits a sigma-type overlapping between the unpaired electrons of the spin carriers and the p-type orbitals of the coordinated N and O atoms producing an electronic delocalization through the bridging ligand responsible for the strong antiferromagnetic interactions observed experimentally.
{"title":"Novel Linear Trinuclear CuII Compound with Trapped Chiral Hemiaminal Ligand: Magnetostructural Study","authors":"C. Cruz, N. Audebrand, D. Páez‐Hernández, V. Paredes-García","doi":"10.3390/magnetochemistry9070175","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070175","url":null,"abstract":"A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat cationic structure [Cu3(HL′)2(H2O)2]4+ with a Cu3 linear core reached by the double Cu-OR/NN-Cu triazole/alkoxo bridge of the hemiaminal molecule. The CuII spin carriers are antiferromagnetically coupled, presenting a spin doublet ground state (S = 1/2) with a magnetic coupling constant of −179 cm−1. Moreover, DTF calculations show that the planarity of the compound permits a sigma-type overlapping between the unpaired electrons of the spin carriers and the p-type orbitals of the coordinated N and O atoms producing an electronic delocalization through the bridging ligand responsible for the strong antiferromagnetic interactions observed experimentally.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42728371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-06DOI: 10.3390/magnetochemistry9070174
R. Kato, T. Tsumuraya
Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this study, we investigated the possibility of Dirac cone formation in two single-component molecular conductors derived from nickel complexes with extended tetrathiafulvalenedithiolate ligands, [Ni(tmdt)2] and [Ni(btdt)2], using tight-biding models and first-principles density-functional theory (DFT) calculations. The tight-binding model predicts the emergence of Dirac cones in both systems, which is associated with the stretcher bond type molecular arrangement. The DFT calculations also indicate the formation of Dirac cones in both systems. In the case of [Ni(btdt)2], the DFT calculations, employing a vdW-DF2 functional, reveal the formation of Dirac cones near the Fermi level in the nonmagnetic state after structural optimization. Furthermore, the DFT calculations, by utilizing the range-separated hybrid functional, confirm the antiferromagnetic stability in [Ni(btdt)2], as observed experimentally.
{"title":"Dirac Cone Formation in Single-Component Molecular Conductors Based on Metal Dithiolene Complexes","authors":"R. Kato, T. Tsumuraya","doi":"10.3390/magnetochemistry9070174","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070174","url":null,"abstract":"Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this study, we investigated the possibility of Dirac cone formation in two single-component molecular conductors derived from nickel complexes with extended tetrathiafulvalenedithiolate ligands, [Ni(tmdt)2] and [Ni(btdt)2], using tight-biding models and first-principles density-functional theory (DFT) calculations. The tight-binding model predicts the emergence of Dirac cones in both systems, which is associated with the stretcher bond type molecular arrangement. The DFT calculations also indicate the formation of Dirac cones in both systems. In the case of [Ni(btdt)2], the DFT calculations, employing a vdW-DF2 functional, reveal the formation of Dirac cones near the Fermi level in the nonmagnetic state after structural optimization. Furthermore, the DFT calculations, by utilizing the range-separated hybrid functional, confirm the antiferromagnetic stability in [Ni(btdt)2], as observed experimentally.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49343515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-02DOI: 10.3390/magnetochemistry9070172
Matheus G. R. Gomes, A. de Souza, H. D. Dos Santos, W. D. De Almeida, D. Paschoal
In the present study, we benchmark computational protocols for predicting Co-59 NMR chemical shift. Quantum mechanical calculations based on density functional theory were used, in conjunction with our NMR-DKH basis sets for all atoms, including Co, which were developed in the present study. The best protocol included the geometry optimization at BLYP/def2-SVP/def2-SVP/IEF-PCM(UFF) and shielding constant calculation at GIAO-LC-ωPBE/NMR-DKH/IEF-PCM(UFF). This computational scheme was applied to a set of 34 Co(III) complexes, in which, Co-59 NMR chemical shift ranges from +1162 ppm to +15,100 ppm, and these were obtained in distinct solvents (water and organic solvents). The resulting mean absolute deviation (MAD), mean relative deviation (MRD), and coefficient of determination (R2) were 158 ppm, 3.0%, and 0.9966, respectively, suggesting an excellent alternative for studying Co-59 NMR.
{"title":"Assessment of a Computational Protocol for Predicting Co-59 NMR Chemical Shift","authors":"Matheus G. R. Gomes, A. de Souza, H. D. Dos Santos, W. D. De Almeida, D. Paschoal","doi":"10.3390/magnetochemistry9070172","DOIUrl":"https://doi.org/10.3390/magnetochemistry9070172","url":null,"abstract":"In the present study, we benchmark computational protocols for predicting Co-59 NMR chemical shift. Quantum mechanical calculations based on density functional theory were used, in conjunction with our NMR-DKH basis sets for all atoms, including Co, which were developed in the present study. The best protocol included the geometry optimization at BLYP/def2-SVP/def2-SVP/IEF-PCM(UFF) and shielding constant calculation at GIAO-LC-ωPBE/NMR-DKH/IEF-PCM(UFF). This computational scheme was applied to a set of 34 Co(III) complexes, in which, Co-59 NMR chemical shift ranges from +1162 ppm to +15,100 ppm, and these were obtained in distinct solvents (water and organic solvents). The resulting mean absolute deviation (MAD), mean relative deviation (MRD), and coefficient of determination (R2) were 158 ppm, 3.0%, and 0.9966, respectively, suggesting an excellent alternative for studying Co-59 NMR.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45331573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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