scholarly journals Communications: Is quantum chemical treatment of biopolymers accurate? Intramolecular basis set superposition error (BSSE)

2010 ◽  
Vol 132 (23) ◽  
pp. 231101 ◽  
Author(s):  
Roman M. Balabin
Keyword(s):  
Chemical Treatment ◽  
Quantum Chemical ◽  
Basis Set ◽  
Basis Set Superposition Error

scholarly journals APPLICATION OF PIEZOSENSORS BASED ON THE MOLECULARLY IMPRINTED POLYIMIDE FOR DETERMI-NATION OF CAFFEINE IN TEA

2021 ◽  
pp. 173-180
Author(s):  
Nhat Linh Cao ◽  
Ol'ga Vasil'yevna Duvanova ◽  
Aleksandr Nikolayevich Zyablov ◽  
Anh Tien Nguyen
Keyword(s):  
Interaction Energy ◽  
Quantum Chemical ◽  
Dft Method ◽  
Basis Set ◽  
Molar Ratio ◽  
Polyamic Acid ◽  
Basis Set Superposition Error ◽  
Molecularly Imprinted ◽  
Relative Standard ◽  
Chemical Simulation

In this article the molecularly imprinted polymers (MIPs) have been synthesized on the surface of piezosensors. The starting polymer for MIPs production was polyamic acid, which is a copolymer of 1,2,4,5-benzenetetracarboxylic acid and 4,4′-diaminodiphenyl ether. The caffeine served as the template. The quantum-chemical simulation was performed by the Gaussian 09 software using the DFT method at the B3LYP/6-31G(d,p) level with the basis set superposition error (BSSE) at the preliminary stage of the synthesis of the MIP for caffeine. The prepolymerization complexes were calculated to establish intermolecular interactions and obtain the optimum molar ratio between the template and polyamiс acid. It is shown that the constitutional repeating units of polyamic acid interact with the caffeine by forming H-bonds via carboxyl groups. The interaction energy first increases and then decreases with increasing the molar ratio of imprinting. Based on the quantum-chemical calculations, the optimal ratio of the reagents in prepolymerization mixture was set to 1 : 3 with the highest interaction energy (96.7 kJ/mol). Applying thermal imidization of solution of polyamic acid in the presence of a template, the molecularly imprinted polyimide has been synthesized by the non-covalent imprinting method. The ability of the obtained piezosensors to recognize the tempalte in model mixtures was experimentally evaluated. It was found that the range of detectable concentrations of caffeine is 3.1.10-6-10-1 mol/dm3 and the detection limit is 10-6 mol/dm3. Correctness of the caffeine determination in model solutions was verified in the spike/recovery tests. Piezosensors based on MIP were approved for the determination of the caffeine in tea varieties. It is shown that the concentration of caffeine in the aqueous solution increases with increasing brewing time. The relative standard deviation is less than 8%.

scholarly journals Oxane dendrimers of tetravalent elements as models for their dioxide polymorphs

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 3-14
Author(s):  
A.G. Grebenyuk ◽  
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Tin Dioxide ◽  
Basis Set ◽  
Basis Sets ◽  
Hydroxyl Groups ◽  
High Symmetry ◽  
Molecular Models ◽  
Basis Set Superposition Error ◽  
Theoretical Approaches

Oxides of tetravalent elements are well known to have a lot of crystalline modifications. For example, most of silica polymorphs are characterized by tetrahedral coordination environment of silicon atoms. On the contrary, crystals of stishovite and of some silicate minerals have their silicon atoms in octahedral coordination spheres. It has been found experimentally that the phase transitions between silica polymorphs accompanied by a rearrangement of silica-oxygen tetrahedrons into octahedra require an energy income (preference energy) of 54 kJ/mol. When increasing the atomic mass of the oxide forming element, the former decreases extremely and for tin dioxide is equal to -59 kJ/mol. These values can be reproduced in a theoretical way, within the frameworks of modern quantum chemical methods and periodic models. High disperse silica nanoparticles (as well as those for other oxides) have only the nearest order of atomic stationing, so that theoretical approaches developed for crystals cannot be applied to small particles. These particles can be transformed into stishovite form under hydrothermal conditions. Such a process can be simulated within cluster approximation by use of molecular models. This work is devoted to quantum chemical simulation of formation of the fragments with hexa-coordinated atoms of silicon and of its analogs in the structure of oxane dendrimers. A row of high symmetry models was examined containing two, three, five, and seventeen atoms of silicon and of germanium, titanium and tin, terminated with hydroxyl groups. These structures can be rearranged into another ones including oxide forming atoms with elevated (equal to 5 or 6) coordination number, so mimicking the rutile-like structure. Such models let it possible to fulfill the procedure of transformation without rupturing siloxane bonds, so remaining within a deformation approach. Another advantage is the exclusion of the basis set superposition error due to use of molecular models of the same total formula for all the coordination states. All calculations were carried out by Hartree-Fock and density functional theory methods with the all-electron (3-21G*) and valent (SBKJC) basis sets by means of the GAMESS program. Models of various size have been examined, in particular, disiloxane (HO)3Si-O-Si(OH)3 witch can be transformed into a self-coordinated form where one of silicon atoms becomes a five-coordinated; trisiloxane (HO)3Si-O-Si(OH)2-O-Si(OH)3 can be rearranged into symmetric isomer with one hexa-coordinated silicon atom. Pentasiloxane with neo-structure of [(HO)3Si-O]4Si forms three coordination structures, the most stable of them mimicking the stishovite crystal; it contains one 6-coordinated and two 5-coordinated silicon atoms. Siloxane containing 17 silicon atoms has a super-neo-structure of {[(HO)3Si-O]3Si-O}4Si; it includes seven six-coordinated and four five-coordinated silicon atoms. Relative models for silicon analogs have been also examined. When analyzing a dependence of the energy differences between open and coordinated oxane structures on the number of atoms of the oxide forming element in the cluster, one can jump to the conclusion that the specific value of this characteristic monotonously decreases with the increase in the number of atoms of the molecular model, so becoming close to the experimental data.

World of van der Waals Species

1993 ◽  
Vol 58 (7) ◽  
pp. 1465-1475
Author(s):  
Pavel Hobza ◽  
Rudolf Zahradník
Keyword(s):  
Chemical Treatment ◽  
Quantum Chemical ◽  
Van Der Waals ◽  
Real Challenge

Van der Waals species (molecules, ions, radicals) attract the attention of chemists, chemical physicists and molecular biologists. Study of these systems presents a real challenge for both experimentalists and theorists. The main features of the contemporary possibilities for quantum chemical treatment are illustrated mostly on systems studied in the authors' laboratory. Prospects in the area are briefly outlined.

On basis set superposition error corrected stabilization energies for large n-body clusters

2011 ◽  
Vol 135 (13) ◽  
pp. 134118 ◽  
Author(s):  
Katarzyna Walczak ◽  
Joachim Friedrich ◽  
Michael Dolg
Keyword(s):  
Basis Set ◽  
Basis Set Superposition Error ◽  
Large N ◽  
Stabilization Energies
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