Temat: quantum chemistry - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Variational quantum eigensolver with reduced circuit complexity
Autorzy:: Tretiak, Sergei
Negre, Christian F. A.
Mniszewski, Susan M.
Anisimov, Petr M.
Cincio, Łukasz
Zhang, Yu
Coles, Patrick J.
Czarnik, Piotr
Dub, Pavel A.
Opis:: The variational quantum eigensolver (VQE) is one of the most promising algorithms to find eigenstates of a given Hamiltonian on noisy intermediate-scale quantum devices (NISQ). The practical realization is limited by the complexity of quantum circuits. Here we present an approach to reduce quantum circuit complexity in VQE for electronic structure calculations. Our ClusterVQE algorithm splits the initial qubit space into clusters which are further distributed on individual (shallower) quantum circuits. The clusters are obtained based on mutual information reflecting maximal entanglement between qubits, whereas inter-cluster correlation is taken into account via a new “dressed” Hamiltonian. ClusterVQE therefore allows exact simulation of the problem by using fewer qubits and shallower circuit depth at the cost of additional classical resources, making it a potential leader for quantum chemistry simulations on NISQ devices. Proof-of-principle demonstrations are presented for several molecular systems based on quantum simulators as well as IBM quantum devices.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 2.

Tytuł:: Employing Range Separation on the meta-GGA Rung: New Functional Suitable for Both Covalent and Noncovalent Interactions
Autorzy:: Hapka, Michał
Szczęśniak, Małgorzata M.
Chałasiński, Grzegorz
Modrzejewski, Marcin
Wydawca:: American Chemical Society
Cytata wydawnicza:: J. Chem. Theory Comput. 12, 3662 (2016); doi: 10.1021/acs.jctc.6b00406
Opis:: We devise a scheme for converting an existing exchange functional into its range-separated hybrid variant. The underlying exchange hole of the Becke-Roussel type has the exact second-order expansion in the interelectron distance. The short-range part of the resulting range-separated exchange energy depends on the kinetic energy density and the Laplacian even if the base functional lacks the dependence on these variables. The most successful practical realization of the scheme, named LC-PBETPSS, combines the range-separated PBE exchange lifted to the hybrid meta-GGA rung and the TPSS correlation. The value of the range-separation parameter is estimated theoretically and confirmed by empirical optimization. The D3 dispersion correction is recommended for all energy computations employing the presented functional. Numerical tests show remarkably robust performance of the method for noncovalent interaction energies, barrier heights, main-group thermochemistry, and excitation energies.
M.M. and M.H. were supported by the Polish Ministry of Science and Higher Education (Grants No. 2014/15/N/ST4/02170 and No. 2014/15/N/ST4/02179). M.M.S. and G.C. were supported by the National Science Foundation (Grant No. CHE-1152474). M.M., M.H., and G.C. gratefully acknowledge additional financial support from the Foundation for Polish Science.
Marcin Modrzejewski
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 3.

Tytuł:: Prediction of the Crystalline Densities of Aliphatic Nitrates by Quantum Chemistry Methods
Autorzy:: Wang, Guixiang
Xu, Yimin
Xue, Chuang
Ding, Zhiyuan
Liu, Yan
Liu, Hui
Gong, Xuedong
Tematy:: aliphatic nitrate
density
quantum chemistry
correlation; Pokaż więcej
Wydawca:: Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:: https://bibliotekanauki.pl/articles/358531.pdf Link otwiera się w nowym oknie
Opis:: Crystal density is a basic and important parameter for predicting the detonation performance of explosives, and nitrate esters are a type of compound widely used in the military context. In this study, thirty-one aliphatic nitrates were investigated using the density functional theory method (B3LYP) in combination with six basis sets (3-21G, 6-31G, 6-31G*, 6-31G**, 6-311G* and 6-31+G**) and the semiempirical molecular orbital method (PM3). Based on the geometric optimizations at various theoretical levels, the molecular volumes and densities were calculated. Compared with the available experimental data, the densities calculated by various methods are all overestimated, and the errors of the PM3 and B3LYP/3-21G methods are larger than those of other methods. Considering the results and the computer resources required by the calculations, the B3LYP/6-31G* method is recommended for predicting the crystalline densities of organic nitrates using a fitting equation. The results obtained with this method are slightly better than those reported by Keshavarz and Rice. In addition, the effects of various groups (such as –ONO2, –OH, –Cl, –O–, and –CH2–) on the densities are also discussed, which is helpful for the design of new molecules in terms of practical requirements.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Counterion effects on the alkali dissolution mechanism of quartz
Autorzy:: Yao, Yu-yun
Tang, Yun
Yang, Yong
Li, Guo-hui
Wu, Bo
Dai, Wen-zhi
Tematy:: quartz
counterion
quantum chemistry
hydrolysis
mechanism; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/2200337.pdf Link otwiera się w nowym oknie
Opis:: In gold ore, quartz plays an important role in mineral formation by acting as the follower. Understanding counterion release, transport, and deposition in alkali solution is a prerequisite for evaluating the potential role of gold separate from quartz deposits in pretreatment. In this work, the aggregation, retention, and release of counterion in alkali solution media were investigated by kinetic research and pure mineral experiments, the correlation and mechanism of these processes were revealed by combining geochemical theory, interaction energy calculation, and quantum chemistry. The results showed that the retention and release of counterion were closely related to the dissolution and corrosion rate of quartz. The NH4+ and Fe2+ with higher mineral affinity reduced the quartz stability, and the dispersion stability and mobility of the quartz were greatly improved by an alkaline substance due to the enhancement of steric hindrance effects. Quantum chemical calculation results show that ammonium ion promotes the dissolution of quartz stronger than ferrous ion, which is mainly reflected in reducing the activation energy required for the formation of transition state (TS1), which can be verified by kinetic calculation. These findings provide essential insight into the extraction of gold coated by quartz as well as a vital reference for the experiment of gold-loaded quartz leaching in mineral processing.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Structure and separation quality of various N- and O-donor ligands from quantum-chemical calculations
Autorzy:: Trumm, M.
Schimmelpfennig, B.
Geist, A.
Tematy:: actinide chemistry
extracting ligands
lanthanide chemistry
quantum chemistry
separation factor; Pokaż więcej
Wydawca:: Instytut Chemii i Techniki Jądrowej
Powiązania:: https://bibliotekanauki.pl/articles/148110.pdf Link otwiera się w nowym oknie
Opis:: Although BTP (2,6-di(1,2,4-triazin-3-yl)pyridine) has been proven to be a highly effective N-donor ligand for the selective An(III)/Ln(III) separation, the origin of its selectivity is still under discussion. We present in this paper quantum-chemical calculations at the density functional theory (DFT) and MP2 level which highlight the role of the aquo ions in the separation process. Furthermore these data will be the reference for future force-field development to investigate the differences in An(III) complexation reactions compared to their Ln(III) counterparts.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Program package MP-ZAVA for parallel quantum-chemical computing in the spd-basis
Autorzy:: Berzigiyarov, P. K.
Zayets, V. A.
Razumov, V. F.
Sheka, E. F.
Tematy:: quantum chemistry
parallel codes
semiempirical approach
spd-basis; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1965900.pdf Link otwiera się w nowym oknie
Opis:: A parallel realization of the NDDO-WF technique for semi-empirical quantum-chemical calculations on large molecular systems in the spd-basis is described. The technological aspects of designing scalable parallel calculations on super computers (by using MPI library) are discussed. The scaling of individual algorithms and entire package was carried out for two model systems with a number of atomic orbitals of 894 and 2014, respectively. The speedup was determined in computer experiments with the RM600 E60 and Cluster Intel PIII multi-processor systems. The effect of communication rate on the package performance is discussed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Theoretical study on molecular structures and spectroscopic properties of tiohydantoins potentially useful for protecting plants against molds and fungi.
Teoretyczne badania struktury i własciwosci spektroskopowych tiohydantoin potencjalnie użytecznych do ochrony roślin przed pleśniami i grzybami.
Autorzy:: Kobyłka, Katarzyna
Opis:: The goal of this work is the determination of molecular structure of two newly synthesized thiohydantoins proposed as new fungicides. The exact structure of these compounds is unknown because they potentially can exist in several tautomeric and geometric (cis-trans isomerism) structures. Geometries of all theoretically possible structures of studied compounds were optimized. Calculations were performed at the Density Functional Theory level using the B3LYP functional and the 6-311++G** basis set. On the base of performed calculations the most probable structure of studied compounds were proposed. Theoretical predictions were verified by comparisons of theoretically calculated IR as well as 1H and 13C NMR spectra with experimental data. It was documented that both studied compounds exist in the tautomeric structure in which the movable hydrogen is connected to the nitrogen atom in the hydantoin ring. Compound 1 (which has only one C=C bond) occurs as one geometric isomer, namely isomer cis. On the other hand, two structures of compound 2 (which has more complicated structure, including two C=C bonds) were observed. Predominates the geometric isomer cis-trans while the second structure population (probably trans-cis) is a bit more than 10%.
Tematem pracy jest wyznaczenie struktury molekularnej dwóch nowo zsyntetyzowanych pochodnych tiohydantoiny proponowanych jako nowe fungicydy. Dokładna struktura badanych związków nie jest znana, ponieważ mogą one występować pod postacią kilku tautomerów i izomerów geometrycznych cis-trans. Zoptymalizowano geometrie wszystkich możliwych struktur obu badanych związków metodą Teorii Funkcjonałów Gęstości przy pomocy funkcjonału B3LYP i bazy funkcyjnej 6-311++G**. Następnie na podstawie różnic energetycznych pomiędzy nimi starano się wytypować te struktury, które powinny występować w rzeczywistości. Przewidywania teoretyczne sprawdzono poprzez porównanie teoretycznych widm IR oraz 1H i 13C NMR z danymi eksperymentalnymi. W wyniku przeprowadzonych badań okazało się, że oba badane związki występują pod postacią tautomeru, w którym labilny proton związany jest z azotem pierścienia hydantoinowego. Związek 1, który posiada jedno wiązanie C=C, występuje pod postacią jednego izomeru geometrycznego, izomeru cis. Natomiast dla bardziej skomplikowanego Związku 2, w którego strukturze mamy dwa wiązania C=C, obserwowane są dwa izomery geometryczne, z których jeden przeważa (cis-trans), a drugi występuje w ilości nieco ponad 10% (prawdopodobnie trans-cis).
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

Inne

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Skocz do pozycji: 8.

Tytuł:: Combined shared and distributed memory ab-initio computations of molecular-hydrogen systems in the correlated state : process pool solution and two-level parallelism
Autorzy:: Kądzielawa, Andrzej
Spałek, Józef
Biborski, Andrzej
Opis:: An efficient computational scheme devised for investigations of ground state properties of the electronically correlated systems is presented. As an example, (H2)n chain is considered with the long-range electron–electron interactions taken into account. The implemented procedure covers: (i) single-particle Wannier wave-function basis construction in the correlated state, (ii) microscopic parameters calculation, and (iii) ground state energy optimization. The optimization loop is based on highly effective process-pool solution — specific root-workers approach. The hierarchical, two-level parallelism was applied: both shared (by use of Open Multi-Processing) and distributed (by use of Message Passing Interface) memory models were utilized. We discuss in detail the feature that such approach results in a substantial increase of the calculation speed reaching factor of 300 for the fully parallelized solution. The scheme elaborated in detail reflects the situation in which the most demanding task is the single-particle basis optimization.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 9.

Tytuł:: Metallization of solid molecular hydrogen in two dimensions : Mott-Hubbard-type transition
Autorzy:: Kądzielawa, Andrzej
Spałek, Józef
Biborski, Andrzej
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 10.

Tytuł:: Degradation mechanism study of amine collectors in Fenton process by quantitative structure-activity relationship analysis
Autorzy:: Wang, X.
Liu, W.
Duan, H.
Tematy:: amine collectors
Fenton process
QSAR
degradation mechanism
quantum chemistry; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/110363.pdf Link otwiera się w nowym oknie
Opis:: In this study, advanced oxidation processes (AOPs), Fenton process, was applied to degrade ten amine collectors. The experimental results indicated that most of the tested amines could be removed rapidly and effectively at pH=4, while the degradation of quaternary ammonium compounds was less than others. To research the Fenton oxidation process, the degradation-rate constants of amine collectors were calculated by the pseudo-second order kinetic model, then which was used as the dependent variable to establish a quantitative structure activity relationship (QSAR) model. Meanwhile, 16 molecular structure descriptors and quantum mechanical parameters for amine collectors were simulated and analyzed by using Materials Studio software. The optimum QSAR model was established based on the partial least squares regression (PLS) method and confirmed by the statistics analysis. The model revealed that hydrogen bond acceptor (HBA) and the maximum values of electrophilic attack in C atom sites (f(-)c) were the major effect factors for the degradation-rate constants of amine collector.
Dostawca treści:: Biblioteka Nauki

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