Synthesis, characterization, DFT calculations and antimicrobial studies of cadmium(II) sulfate complexes of thioureas and 2-mercaptopyridine; X-ray structures of polymeric diaqua(N,N′-dimethylthiourea) sulfatocadmium(II) and bis(2-mercaptopyridine)sulfatocadmium(II)
TL;DR: In this article, the properties of the Cadmium(II) complexes of thioureas, [Cd(Tu)(SO4)(H2O)2]n (1), [Ccd(Dmtu)2(SO4), H2O 2, H2 O 2 ]n (2) and Mpy 2(Mpy) 2(SO 4 )n (3) were characterized by IR and NMR spectroscopy, and thermal analysis.
About: This article is published in Polyhedron.The article was published on 2018-07-15. It has received 2 citations till now. The article focuses on the topics: Nuclear magnetic resonance spectroscopy.
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TL;DR: The non-ionic [Ag(Tu)(CN)] complex formation was explained with the largest bonding capacity of the sulfur donor atom of Tu ligand and the strongest covalent and donor-acceptor Ag–S(Tu) interaction.
Abstract: The structures of non-ionic [Ag(Tu)(CN)] (1) and ionic [Ag(Dmtu)2]+[Ag(CN)2]− (2) and [Ag(Imt)2]+[Ag(CN)2]− (3) silver(I) complexes, where Tu = thiourea, Dmtu = N,N′-dimethylthiourea and Imt = imidazoline-2-thione), were modeled by periodic DFT/PAW-PBE calculations; results were in good agreement with experiments. The bonding ability of the thiourea ligands (Tu, Dmtu and Imt) and the rival Ag–C, Ag–S, Ag–N and Ag–Ag bonds were estimated by natural population analysis and natural bonding orbital calculations. The metal–ligand bond strengths were found to decrease in the following order Ag-CCN > Ag-Sthiourea > Ag–NCN, and the main bonding contribution was covalent, donor–acceptor and electrostatic, respectively. The non-ionic [Ag(Tu)(CN)] complex formation [distinguished from the ionic Ag(I) complexes] was explained with the largest bonding capacity of the sulfur donor atom of Tu ligand and the strongest covalent and donor-acceptor Ag–S(Tu) interaction. The infrared (IR) spectra of the experimentally observed structures were reliably interpreted and the IR vibrations, which were sensitive to the ligand coordination to Ag(I) ion and to the weak intra- and intermolecular interactions, were selected with the help of DFT frequency calculations in the solid state.
9 citations
19 Mar 2021
TL;DR: Luminescent trans-[Pb(DMTU-S)4Cl2] (dMTU: N,N′-dimethylthiourea) was designed and prepared via either mechanochemical or solvothermal methods as mentioned in this paper.
Abstract: Luminescent trans-[Pb(DMTU-S)4Cl2] (DMTU: N,N′-dimethylthiourea) was designed and prepared via either mechanochemical or solvothermal methods, and the structures of DMTU and trans-[Pb(DMTU-S)4Cl2] ...
3 citations
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
TL;DR: This paper could serve as a general literature citation when one or more of the open-source SH ELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
Abstract: An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
81,116 citations
TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.
Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
57,691 citations
TL;DR: In this paper, the authors present an ab initio quantum-mechanical molecular-dynamics calculations based on the calculation of the electronic ground state and of the Hellmann-Feynman forces in the local density approximation.
Abstract: We present ab initio quantum-mechanical molecular-dynamics calculations based on the calculation of the electronic ground state and of the Hellmann-Feynman forces in the local-density approximation at each molecular-dynamics step. This is possible using conjugate-gradient techniques for energy minimization, and predicting the wave functions for new ionic positions using subspace alignment. This approach avoids the instabilities inherent in quantum-mechanical molecular-dynamics calculations for metals based on the use of a fictitious Newtonian dynamics for the electronic degrees of freedom. This method gives perfect control of the adiabaticity and allows us to perform simulations over several picoseconds.
32,798 citations