Wydział Chemii (WCh)/Faculty of Chemistry

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THE NUCLEAR MAGNETIC SHIELDING AND SPIN-ROTATION CONSTANTS OF THE HYDROGEN MOLECULE
(Elsevier, 1995-04-07) Komasa, Jacek; Rychlewski, Jacek; Raynes, William T.
The variation-perturbation method, employing an explicitly correlated basis set in the form of Gaussian functions with exponential correlation factors, has been used to calculate the paramagnetic component of the nuclear magnetic shielding and the electronic contribution to the spin-rotation constant for the hydrogen molecule in its ground state. The diamagnetic components of the shielding tensor have also been computed. The computations have been performed for three internuclear distances in the vicinity of equilibrium. A comparison of the calculated quantities, which are of high accuracy, with the experimental data reveals a small but significant discrepancy between theory and experiment.
FT-TR, UV-VISIBLE AND X-RAY STUDIES OF COMPLEXES OF PYRIDINE N-OXIDES WITH PENTACHLOROPHENOL
(1995-11-01) Dega-Szafran, Zofia; Grunwald-Wyspianska, Monika; Kania, Anna; Kosturkiewicz, Zofia; Tykarska, Ewa; Szafran, Mirosław
The crystal structure of the 4-methoxy-2,6-dimethylpyridine N-oxide pentachlorophenol complex has been determined by X-ray analysis. The O ... O distance is 2.439(6) Angstrom, the OHO angle is 152.3 degrees and the hydrogen-bonded proton is close to the phenol molecule. The FT-IR spectra of pentachlorophenol complexes with some substituted pyridine N-oxides in the solid state and seven aprotic solvents of different polarity (epsilon from 2.27 to 37.5) show a broad absorption. The broad absorption shows weak dependence upon solvent polarity and is classified as type (ii). UV spectra show that in the investigated complexes protons are not transferred from the phenol to the N-oxides. Formamide (epsilon = 111) is a much stronger proton acceptor than the pyridine N-oxides. Pentachlorophenol in formamide is converted to the phenolate ion.
The ground state of (He-H-He)(+) from correlated ab initio calculations
(POLISH CHEMICAL SOCIETY, 1998-07) Komasa, Jacek; Rychlewski, Jacek
He2H+ ion in its ground state is studied by means of ab initio methods taking into account the electron correlation. Geometry optimization at the CCSD(T)/cc-pV5Z level of theory has been performed and the potential energy hypersurface scan is presented. The optimum conformation is linear and symmetric with the proton at the He-He midpoint and the He-H distance equal to 1.75 bohr. Stabilization energy with respect to the He2H+ --> HeH+ + He dissociation channel has been computed. Additionally, a single point variational calculations with the use of the Exponentially Correlated Gaussian wave functions have been performed. They supply an upper bound to both the total electronic energy (-5.903505 hartree) and the stabilization energy (-13.224 kcal/mol). A comparison of the results from both the perturbational coupled cluster and variational methods is presented.
Exponentially correlated Gaussian functions in variational calculations. Momentum space properties of the ground state helium dimer
(American Institute of Physics, 2001-07-01) Komasa, Jacek
Microhartree accuracy wave functions composed of exponentially correlated Gaussians were transformed in closed form to momentum space representation and applied to compute various isotropic momentum space properties of helium dimer in the ground state. The set of properties includes electron momentum density distribution, expectation values of powers of the electronic momentum operator, and the Compton profile. Calculations were performed at many internuclear separations R including the united atom (beryllium) and the separated atoms (helium) limits.
Dipole and quadrupole polarizabilities and shielding factors of beryllium from exponentially correlated Gaussian functions
(American Physical Society, 2001-12-14) Komasa, Jacek
Dynamic dipole and quadrupole polarizabilities as well as shielding factors of the beryllium atom in the ground state were computed at real frequencies by using the variation-perturbation method. The zeroth- and the first-order wave functions were expanded in many-electron basis of exponentially correlated Gaussian functions. The 1600-term expansion of the unperturbed wave function yielded the ground-state energy accurate to 1 cm-1. The first-order wave functions were expanded in very large bases (4800 and 4400 terms). The nonlinear parameters of the first-order correction functions were optimized with respect to both the static and dynamic polarizabilities, and with respect to the excited-state energies. The procedure employed ensures a high accuracy of determination of dynamic properties in a wide range of frequencies and correct positions of the transition poles. Test calculations, performed on He and Li, confirmed the ability of this method to obtain the atomic properties with very high accuracy. The final values of the static properties of Be were 37.755 e2a02EH-1 and 300.96 e2a04EH-1 for the dipole and quadrupole polarizabilities, respectively, and 1.4769 for the quadrupole shielding factor. The convergence of the atomic properties with the size of the expansion of both the zeroth- and first-order functions was checked. Thanks to very high accuracy of the unperturbed wave function and the efficient method of construction of the first-order wave functions, the dynamic polarizability results presented in this work are of benchmark quality. As a by-product of this project, a set of the most accurate upper bounds to the energies of 1P and 1D states of Be was obtained.
Bethe logarithm for the lithium atom from exponentially correlated Gaussian functions
(AMERICAN PHYSICAL SOCIETY, 2003-10-27) Pachucki, Krzysztof; Komasa, Jacek
The calculation of Bethe logarithm for the ground state of the lithium atom is presented. The Bethe logarithm is the main QED effect coming from the electron self-interaction, which has not been obtained yet. Both results for the infinite nuclear mass, ln k = 5.178 17(3), and the mass polarization correction, Delta ln k = 0.114(3), significantly improve the hitherto theoretical values for the lithium ground-state energy. They allow from one side to test the theory against precise measurements of transition frequencies and from the other side, to improve the accuracy of determination of the difference in the square of nuclear charge radii from the isotope-shift measurements. The applied calculational method is based on the well adapted explicitly correlated Gaussian basis set and can be extended to other few-electron atoms and molecules.
A new approach to Kołos-Wolniewicz wave functions
(Polish Chemical Society, 2004) Kubacki, Tomasz; Komasa, Jacek
The Kołos-Wolniewicz (KW) wave functions are well known in quantum chemistry. In this work we study a possibility of generalization of KW functions towards greater flexibility and compactness. We report on a new approach to evaluation of integrals which allows numerical integration to be avoided. Some preliminary results illustrating an acceleration in energy convergence are reported.
Relativistic and QED Corrections for the Beryllium Atom
(American Physical Society, 2004) Pachucki, Krzysztof; Komasa, Jacek
Complete relativistic and quantum electrodynamics corrections of order α2 Ry and α3 Ry are calculated for the ground state of the beryllium atom and its positive ion. A basis set of correlated Gaussian functions is used, with exponents optimized against nonrelativistic binding energies. The results for Bethe logarithms lnk0(Be)=5.750 34(3) and lnk0(Be+)=5.751 67(3) demonstrate the availability of high precision theoretical predictions for energy levels of the beryllium atom and light ions. Our recommended value of the ionization potential 75 192.514(80) cm-1 agrees with equally accurate available experimental values.
Exponentially correlated Gaussian functions in variational calculations. The EF singlet-Sigma-g-+ state of hydrogen molecule
(scientific Publishers OWN, 2004) Komasa, Jacek; Cencek, Wojciech
The Born-Oppenheimer (BO) potential energy curve, the adiabatic and the relativistic corrections for the EF state of the hydrogen molecule are calculated for the internuclear distances ranging from 0.01 to 20 bohr. 600-term variational expansions of exponentially correlated Gaussian (ECG) functions are used. The BO energies and the adiabatic corrections are more accurate than previously reported and the relativistic calculations confirm existing literature values.
On the acceleration of the convergence of singular operators in Gaussian basis sets
(AMERICAN INSTITUTE OF PHYSICS, 2005-05-08) Pachucki, Krzysztof; Cencek, Wojciech; Komasa, Jacek
Gaussian type wave functions do not reproduce the interparticle cusps which result in a slow convergence of the expectation values of the operators involved in calculations of the relativistic and QED energy corrections. Methods correcting this deficiency are the main topic discussed in this paper. Benchmark expectation values of the singular operators for several few-electron systems are presented.
Excitation energy of 9Be
(American Physical Society, 2006-05) Pachucki, Krzysztof; Komasa, Jacek
The high precision relativistic and radiative corrections to the energy of the excited 3 S-1 state of the beryllium atom are obtained. The nonrelativistic wave function, expanded in a basis of exponentially correlated Gaussian functions, yields the lowest upper bounds to the energy of 2 S-1 and 3 S-1 states. By means of the integral representation, a reference-quality Bethe logarithm has been obtained. The resulting theoretical 2 S-1-3 S-1 transition energy amounts to 54 677.78(45) cm(-1) and differs from the known experimental value by about 0.5 cm(-1).
Molecular structure of 8-hydroxy-1-methylquinolinium iodide hydrate in crystal and solution
(2006-06-29) Barczyński, Piotr; Komasa, Anna; Ratajczak-Sitarz, Małgorzata; Katrusiak, Andrzej; Brzezinski, Bogumil
8-Hydroxy-1-methylquinolinium iodide monohydrate [(C10H10NO)I-+(-) H2O] has been studied by X-ray diffraction, FF-IR, H-1 and C-13 NMR spectroscopy. In the crystalline state, the iodide anion is hydrogen-bonded to the water molecule, which in turn is hydrogen bonded to the 8-OH group of the 8-hydroxyquinolinium ring, forming of a symmetric dimer. In acetonitrile and DMSO-d(6) the hydrate assumes a new structure due to almost complete dissociation of the water molecule from the complex structure. In acetonitrile the 8-OH group is hydrogen-bonded to the iodide anion, whereas in DMSO-d(6) it forms the hydrogen bond with the solvent molecules. This 8-OH... O(DMSO-d(6)) hydrogen bond is the strongest within the structure of the hydrate.
Dealing with communicative problems in English as a lingua franca
(Vilnius University Publishing House, 2008) Nowicka, Agnieszka
These days English happens to be one of the most widely used languages of international communication. Speakers communicating in English as a lingua franca have a diverse linguistic command of it. However, these are not only the problems of linguistic (structural) origin that speakers need to deal with while interacting in English. In the article, I aim to discuss, first, how the differences in socio-cultural interaction styles can influence communication, second, what is interaction participants’ orientation to the problems originating in those differing styles and, finally, how such problems are negotiated in communication. Ethnomethodological conversation analysis is used to analyze illustrative excerpt of interaction in English.
Ortho-para transition in molecular hydrogen
(American Physical Society, 2008-03-14) Pachucki, Krzysztof; Komasa, Jacek
The radiative ortho-para transition in molecular hydrogen is studied. This highly forbidden transition is very sensitive to relativistic and subtle nonadiabatic effects. Our result for the transition rate in the ground vibrational level Γ(J=1→J=0)=6.20(62)×10−14 yr−1 is significantly lower in comparison to all the previous approximate calculations. Experimental detection of such a weak line by observation of, for example, cold interstellar molecular hydrogen is at present unlikely.
The Sigma- states of the molecular hydrogen
(The Royal Society of Chemistry, 2008-05-08) Komasa, Jacek
A class of doubly excited electronic states of the hydrogen molecule is reported. The states are of Sigma− symmetry and are located ca. 200000 cm−1 above the ground state and about 75000 cm−1 above the ionization threshold. The electronic wave functions employed to described these states have been expanded in the basis of exponentially correlated Gaussian (ECG) functions with the nonlinear parameters variationally optimized. The lowest triplet-Sigma−g and singlet-Sigma−u states dissociate into hydrogen atoms in the n = 2 state, whereas the lowest triplet-Sigma−u and singlet-Sigma−g states have H(n = 2) and H(n = 3) as the dissociation products. All the four states are attractive and accommodate vibrational levels. The location of the vibrational energy levels has been determined by solving the radial Schrödinger equation within the Born–Oppenheimer approximation.
Molecular structure, hydrogen bonding and spectroscopic properties of the complex of piperidine-4-carboxylic acid with chloroacetic acid
(2008-10-29) Komasa, Anna; Katrusiak, Andrzej; Szafran, Mirosław; Barczyński, Piotr; Dega-Szafran, Zofia
Complex of piperidine-4-carboxylic acid with chloroacetic acid has been studied by X-ray diffraction, FTIR, Raman, H-1 and C-13 NMR spectroscopy and B3LYP/6-31G(d,p) calculations. In crystal the piperidine ring is protonated and adopts a chair conformation with the COOH group in the equatorial position. The COO- group of chloroacetate unit is engaged in three hydrogen bonds: O(1)-H(1)center dot center dot center dot O(3) of 2.604(2) angstrom, N(1)-H(12)center dot center dot center dot O(3) of 2.753(2) angstrom and N(1)-H(11)center dot center dot center dot O(4) of 2.760(2) angstrom. According to the B3LYP calculations the isolated complexes both in vacuum and H2O solution have cyclic structures. In vacuum the molecules are connected by two H-bonds: the COOH group of chloroacetic acid is engaged with piperidine-4-carboxylic acid, one with the nitrogen atom, O(4)-H center dot center dot center dot N(1) of 2.658 angstrom and the second with carboxyl group, O(1)-H center dot center dot center dot O(3) of 2.860 angstrom. In water solution piperidine-4-carboxylic acid is protonated and forms two hydrogen bonds with the chloroacetate unit: N(1)-H center dot center dot center dot O(4) of 2.690 angstrom and O(1)-H center dot center dot center dot O(3) of 2.611 angstrom. Powder FTIR spectra of the complex and its deuterated analogue are consistent with the X-ray structure. Correlations between the experimental H-1 and C-13 chemical shifts of the complex investigated and the GIAO/B3LYP/6-31G(d,p) calculated magnetic isotropic shielding tensors (sigma(calc)) in vacuum and within the conductor-like screening continuum solvation model (COSMO) in H2O, delta(exp) = a + b sigma(calc), are reported.
Nonadiabatic corrections to rovibrational levels of H2
(American Institute of Physics, 2009) Pachucki, Krzysztof; Komasa, Jacek
The leading nonadiabatic corrections to rovibrational levels of a diatomic molecule are expressed in terms of three functions of internuclear distance: corrections to the adiabatic potential, the effective nuclear mass, and the effective moment of inertia. The resulting radial Schrödinger equation for nuclear motion is solved numerically yielding accurate nonadiabatic energies for all rovibrational levels of the H2 molecule. Results for states with J ≤ 10 are in excellent agreement with previous calculations by Wolniewicz, and for states with J>10 are new.
Rovibrational levels of HD
(ROYAL SOCIETY OF CHEMISTRY, 2010) Pachucki, Krzysztof; Komasa, Jacek
The dissociation energies of all rotation-vibrational states of the molecular HD in the ground electronic state are calculated to a high accuracy by including nonadiabatic, relativistic alpha(2), and quantum electrodynamic alpha(3) effects, with approximate treatment of small higher order alpha(4), and finite nuclear size corrections. The obtained result for the ground molecular state of 36 405.7828(10) cm(-1) is in a small disagreement with the latest most precise experimental value.
Synteza i aktywność katalityczna siloksylowych kompleksów rutenu
(2010-01-21T11:53:05Z) Rogalski, Szymon; Marciniec, Bogdan. Promotor
Zrealizowana praca doktorska dotyczyła syntezy nowych siloksylowych kompleksów rutenu i ich zastosowania jako katalizatorów w wybranych reakcjach katalitycznych. W wyniku przeprowadzonych badań opracowano efektywne metody syntezy 10 nowych siloksylowych kompleksów Ru. Eksperymenty skoncentrowane były głównie na otrzymaniu alkilidenowych kompleksów siloksylowych Ru i zastosowaniu ich jako efektywnych katalizatorów metatezy olefin. Otrzymano także siloksylowe kompleksy cyklopentadienylowe i arenowe rutenu, które zastosowano jako efektywne katalizatory reakcji hydrosililowania wybranych olefin. Otrzymano także siloksylowy kompleks hydrydowy rutenu, który przetestowano w reakcji sililującego sprzęgania. Otrzymano pierwszy alkilidenowy kompleks rutenu, oparty na katalizatorze Hoveydy-Grubbsa 2 generacji, połączony bezpośrednim wiązaniem Ru-O-Si z powierzchnią krzemionki. Immobilizowany kompleks scharakteryzowano za pomocą spektroskopii NMR w ciele stałym. Osadzony na krzemionce kompleks zastosowano jako efektywny katalizator w wybranych procesach metatetycznych. Heterogenizowany kompleks alkilidenowy może być z powodzeniem odzyskany i użyty ponownie. W reakcji metatezy z zamknięciem pierścienia dietylomalonianu diallilu wykonano 15 cykli katalitycznych bez zmniejszenia wydajności reakcji. Udowodniono minimalne wymywanie katalizatora z powierzchni krzemionki podczas reakcji.
Utleniające odwodornienie lekkich parafin na zeolitach modyfikowanych metalami przejściowymi
(2010-05-21T07:33:19Z) Kowalska-Kuś, Jolanta; Nowińska, Krystyna. Promotor
Badania podjęte w pracy doktorskiej dotyczyły procesu utleniającego odwodornienia (ODH) węglowodorów C2-C4 na sitach molekularnych, głównie zeolitach, modyfikowanych metalami przejściowymi, przede wszystkim żelazem, w obecności tlenku diazotu jako utleniacza. Do głównych zadań realizowanych w pracy należą: 1. ocena wpływu matrycy (stosowano matryce zeolitowe o różnej strukturze, matryce mezoporowate oraz matryce niezeolitowe), na aktywność kompleksów żelaza w reakcji utleniającego odwodornienia lekkich parafin; 2. ocena wpływu modyfikatora (modyfikacja żelazem lub wanadem) na aktywność utleniającą układu; 3. ocena wpływu parametrów charakteryzujących katalizatory (stosunek Si/Al, temperatura prażenia) na kierunek przemian utlenianych węglowodorów; 4. ocena wpływu zawartości żelaza oraz kwasowości katalizatorów na ich aktywność utleniającą; 5. ocena kwasowości badanych próbek na podstawie TPD amoniaku oraz widm IR adsorbowanej pirydyny oraz aktywności w reakcji modelowej krakingu kumenu; 6. badanie wpływu stopniowej eliminacji centrów kwasowych zeolitów Fe-ZSM-5 (zatruwanie sodem) na aktywność w reakcji ODH etanu i propanu oraz na selektywność do poszczególnych produktów; 7. badanie struktury aktywnych kompleksów żelaza generowanych w zeolitach na podstawie widm FT-IR adsorbowanego NO, który stosowany był jako cząsteczka sonda, jak również na podstawie pomiarów technikami EPR, UV-Vis, TPR-H2, 8. badanie mechanizmu oddziaływania centrów aktywnych z reagentami (alkan i N2O) poprzez wykorzystanie technik spektroskopowych (badania FT-IR prowadzone in situ).

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