The Experts below are selected from a list of 333 Experts worldwide ranked by ideXlab platform
Ludwik Adamowicz - One of the best experts on this subject based on the ideXlab platform.
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the 2s rydberg series of the Lithium Atom calculations with all electron explicitly correlated gaussian functions
Chemical Physics Letters, 2019Co-Authors: Amir Bralin, Sergiy Bubin, Ludwik Adamowicz, Monika StankeAbstract:Abstract In this work we report very accurate variational calculations of the twelve lowest 2 S Rydberg states of the Lithium Atom performed with the finite-nuclear-mass (FNM) approach and with all-electron explicitly correlated Gaussian functions. The FNM non-relativistic variational energies of the states are augmented with the leading relativistic and QED corrections. The calculated transition energies are compared with the previous works (only eight states of the series were calculated before) and with the available experimental results. Density distributions of the electrons and the nucleus in the center-of-mass frame are also shown.
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Lower Rydberg 2 F states of the Lithium Atom: Finite-nuclear-mass calculations with explicitly correlated Gaussian functions
Molecular Physics, 2013Co-Authors: Keeper L Sharkey, Ludwik AdamowiczAbstract:Variational non-relativistic calculations are performed for the four lowest Rydberg 2F states (1s2nf, n = 4, … , 7) of the main isotope of the Lithium Atom (7Li). The finite-nuclear-mass approach is employed and the wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian function. A total of 140 Gaussians are used for each state. The calculated relative energy of the two lowest states is compared with the experimental value, which is the only value available in the literature. The two results agree within a few wavenumbers.
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an algorithm for quantum mechanical finite nuclear mass variational calculations of Atoms with l 3 using all electron explicitly correlated gaussian basis functions
Journal of Chemical Physics, 2013Co-Authors: Keeper L Sharkey, Nikita Kirnosov, Ludwik AdamowiczAbstract:A new algorithm for quantum-mechanical nonrelativistic calculation of the Hamiltonian matrix elements with all-electron explicitly correlated Gaussian functions for Atoms with an arbitrary number of s electrons and with three p electrons, or one p electron and one d electron, or one f electron is developed and implemented. In particular the implementation concerns Atomic states with L = 3 and M = 0. The Hamiltonian used in the approach is obtained by rigorously separating the center-of-mass motion from the laboratory-frame all particle Hamiltonian, and thus it explicitly depends on the finite mass of the nucleus. The approach is employed to perform test calculations on the lowest 2F state of the two main isotopes of the Lithium Atom, 7Li and 6Li.
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explicitly correlated gaussian calculations of the 2p o rydberg spectrum of the Lithium Atom
Journal of Chemical Physics, 2012Co-Authors: Sergiy Bubin, Ludwik AdamowiczAbstract:Accurate quantum-mechanical nonrelativistic variational calculations are performed for the nine lowest members of the 2Po Rydberg series (1s2np1, n = 2, …, 10) of the Lithium Atom. The effect of the finite nuclear mass is included in the calculations allowing for determining the isotopic shifts of the energy levels. The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions. The exponential parameters of the Gaussians are variationally optimized with the aid of the analytical energy gradient determined with respect to those parameters. The calculated state energies are compared with the available experimental data.
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refinement of the experimental energy levels of higher 2d rydberg states of the Lithium Atom with very accurate quantum mechanical calculations
Journal of Chemical Physics, 2011Co-Authors: Keeper L Sharkey, Sergiy Bubin, Ludwik AdamowiczAbstract:Very accurate variational non-relativistic calculations are performed for four higher Rydberg 2D states (1s2nd1, n = 8, …, 11) of the Lithium Atom (7Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the 2S 1s22s1 ground state.
Keeper L Sharkey - One of the best experts on this subject based on the ideXlab platform.
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Lower Rydberg 2 F states of the Lithium Atom: Finite-nuclear-mass calculations with explicitly correlated Gaussian functions
Molecular Physics, 2013Co-Authors: Keeper L Sharkey, Ludwik AdamowiczAbstract:Variational non-relativistic calculations are performed for the four lowest Rydberg 2F states (1s2nf, n = 4, … , 7) of the main isotope of the Lithium Atom (7Li). The finite-nuclear-mass approach is employed and the wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian function. A total of 140 Gaussians are used for each state. The calculated relative energy of the two lowest states is compared with the experimental value, which is the only value available in the literature. The two results agree within a few wavenumbers.
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an algorithm for quantum mechanical finite nuclear mass variational calculations of Atoms with l 3 using all electron explicitly correlated gaussian basis functions
Journal of Chemical Physics, 2013Co-Authors: Keeper L Sharkey, Nikita Kirnosov, Ludwik AdamowiczAbstract:A new algorithm for quantum-mechanical nonrelativistic calculation of the Hamiltonian matrix elements with all-electron explicitly correlated Gaussian functions for Atoms with an arbitrary number of s electrons and with three p electrons, or one p electron and one d electron, or one f electron is developed and implemented. In particular the implementation concerns Atomic states with L = 3 and M = 0. The Hamiltonian used in the approach is obtained by rigorously separating the center-of-mass motion from the laboratory-frame all particle Hamiltonian, and thus it explicitly depends on the finite mass of the nucleus. The approach is employed to perform test calculations on the lowest 2F state of the two main isotopes of the Lithium Atom, 7Li and 6Li.
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refinement of the experimental energy levels of higher 2d rydberg states of the Lithium Atom with very accurate quantum mechanical calculations
Journal of Chemical Physics, 2011Co-Authors: Keeper L Sharkey, Sergiy Bubin, Ludwik AdamowiczAbstract:Very accurate variational non-relativistic calculations are performed for four higher Rydberg 2D states (1s2nd1, n = 8, …, 11) of the Lithium Atom (7Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the 2S 1s22s1 ground state.
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Lower Rydberg 2D states of the Lithium Atom: Finite-nuclear-mass calculations with explicitly correlated Gaussian functions
Physical Review A, 2011Co-Authors: Keeper L Sharkey, Sergiy Bubin, Ludwik AdamowiczAbstract:Very accurate variational nonrelativistic calculations are performed for the five lowest Rydberg {sup 2}D states (1s{sup 2}nd{sup 1}, n=3,...,7) of the Lithium Atom ({sup 7}Li). The finite-nuclear-mass approach is employed and the wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian function. Four thousand Gaussians are used for each state. The calculated relative energies of the states determined with respect to the {sup 2}S 1s{sup 2}2s{sup 1} ground state are systematically lower than the experimental values by about 2.5 cm{sup -1}. As this value is about the same as the difference between the experimental relative energy between {sup 7}Li{sup +} and {sup 7}Li in their ground-state energy and the corresponding calculated nonrelativistic relative energy, we attribute it to the relativistic effects not included in the present calculations.
Sergiy Bubin - One of the best experts on this subject based on the ideXlab platform.
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the 2s rydberg series of the Lithium Atom calculations with all electron explicitly correlated gaussian functions
Chemical Physics Letters, 2019Co-Authors: Amir Bralin, Sergiy Bubin, Ludwik Adamowicz, Monika StankeAbstract:Abstract In this work we report very accurate variational calculations of the twelve lowest 2 S Rydberg states of the Lithium Atom performed with the finite-nuclear-mass (FNM) approach and with all-electron explicitly correlated Gaussian functions. The FNM non-relativistic variational energies of the states are augmented with the leading relativistic and QED corrections. The calculated transition energies are compared with the previous works (only eight states of the series were calculated before) and with the available experimental results. Density distributions of the electrons and the nucleus in the center-of-mass frame are also shown.
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explicitly correlated gaussian calculations of the 2p o rydberg spectrum of the Lithium Atom
Journal of Chemical Physics, 2012Co-Authors: Sergiy Bubin, Ludwik AdamowiczAbstract:Accurate quantum-mechanical nonrelativistic variational calculations are performed for the nine lowest members of the 2Po Rydberg series (1s2np1, n = 2, …, 10) of the Lithium Atom. The effect of the finite nuclear mass is included in the calculations allowing for determining the isotopic shifts of the energy levels. The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions. The exponential parameters of the Gaussians are variationally optimized with the aid of the analytical energy gradient determined with respect to those parameters. The calculated state energies are compared with the available experimental data.
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refinement of the experimental energy levels of higher 2d rydberg states of the Lithium Atom with very accurate quantum mechanical calculations
Journal of Chemical Physics, 2011Co-Authors: Keeper L Sharkey, Sergiy Bubin, Ludwik AdamowiczAbstract:Very accurate variational non-relativistic calculations are performed for four higher Rydberg 2D states (1s2nd1, n = 8, …, 11) of the Lithium Atom (7Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the 2S 1s22s1 ground state.
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Lower Rydberg 2D states of the Lithium Atom: Finite-nuclear-mass calculations with explicitly correlated Gaussian functions
Physical Review A, 2011Co-Authors: Keeper L Sharkey, Sergiy Bubin, Ludwik AdamowiczAbstract:Very accurate variational nonrelativistic calculations are performed for the five lowest Rydberg {sup 2}D states (1s{sup 2}nd{sup 1}, n=3,...,7) of the Lithium Atom ({sup 7}Li). The finite-nuclear-mass approach is employed and the wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian function. Four thousand Gaussians are used for each state. The calculated relative energies of the states determined with respect to the {sup 2}S 1s{sup 2}2s{sup 1} ground state are systematically lower than the experimental values by about 2.5 cm{sup -1}. As this value is about the same as the difference between the experimental relative energy between {sup 7}Li{sup +} and {sup 7}Li in their ground-state energy and the corresponding calculated nonrelativistic relative energy, we attribute it to the relativistic effects not included in the present calculations.
Oliver Oeckler - One of the best experts on this subject based on the ideXlab platform.
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Lithium Atom mobility in Lithium germanium antimony tellurides elucidated by neutron diffraction and quasielastic neutron scattering
Journal of Alloys and Compounds, 2020Co-Authors: Stefan Schwarzmuller, Markus Hoelzel, Katharina Fritsch, Zachary Evenson, Klaus Habicht, Oliver OecklerAbstract:Abstract Lithium germanium antimony tellurides are known as promising thermoelectric materials. Earlier 7Li solid state NMR studies had revealed pronounced Lithium Atom mobility. Further insights into the diffusion mechanism are investigated by means of neutron powder diffraction in combination with quasielastic neutron scattering (QENS). In vacancy-containing LiGe3.5Sb2Te7, the isotropic displacement parameters of the cations are larger than in vacancy-free Li2Ge3Sb2Te7 and thus indicate more pronounced Atom mobility in the investigated temperature range from room temperature to 600 °C. In contrast, temperature-dependent isotropic displacement parameters of the anions are similar for both solid solutions. Comparable to the situation in the important thermoelectric material PbTe, anharmonic displacement parameters for LiGe3.5Sb2Te7 – a Lithium germanium antimony telluride with optimized thermoelectric properties – are significant already at room temperature. The extrapolation of displacement parameters toward low temperatures indicates that the displacements are predominantly dynamic. The temperature-dependent evaluation of lattice parameters and isotropic displacement parameters reveals three different regimes. From room temperature to 250 °C, a NaCl-type model with anharmonic displacement parameters for cation sites fits well. Between 250 °C and 400 °C, the unit cell volume increases less than in the other regimes and small lattice distortions may occur. At temperatures higher than 400 °C (investigated up to 600 °C), Lithium Atoms also occupy tetrahedral voids of the fcc Te substructure. Whereas QENS data probing the picosecond time scale show no significant Lithium Atom mobility in the Q range of 0.08–1.68 A−1, a temperature-dependent change in the elastic scattering term hints at a different time window or a combination of motions with different time scales.
Klaus Habicht - One of the best experts on this subject based on the ideXlab platform.
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Lithium Atom mobility in Lithium germanium antimony tellurides elucidated by neutron diffraction and quasielastic neutron scattering
Journal of Alloys and Compounds, 2020Co-Authors: Stefan Schwarzmuller, Markus Hoelzel, Katharina Fritsch, Zachary Evenson, Klaus Habicht, Oliver OecklerAbstract:Abstract Lithium germanium antimony tellurides are known as promising thermoelectric materials. Earlier 7Li solid state NMR studies had revealed pronounced Lithium Atom mobility. Further insights into the diffusion mechanism are investigated by means of neutron powder diffraction in combination with quasielastic neutron scattering (QENS). In vacancy-containing LiGe3.5Sb2Te7, the isotropic displacement parameters of the cations are larger than in vacancy-free Li2Ge3Sb2Te7 and thus indicate more pronounced Atom mobility in the investigated temperature range from room temperature to 600 °C. In contrast, temperature-dependent isotropic displacement parameters of the anions are similar for both solid solutions. Comparable to the situation in the important thermoelectric material PbTe, anharmonic displacement parameters for LiGe3.5Sb2Te7 – a Lithium germanium antimony telluride with optimized thermoelectric properties – are significant already at room temperature. The extrapolation of displacement parameters toward low temperatures indicates that the displacements are predominantly dynamic. The temperature-dependent evaluation of lattice parameters and isotropic displacement parameters reveals three different regimes. From room temperature to 250 °C, a NaCl-type model with anharmonic displacement parameters for cation sites fits well. Between 250 °C and 400 °C, the unit cell volume increases less than in the other regimes and small lattice distortions may occur. At temperatures higher than 400 °C (investigated up to 600 °C), Lithium Atoms also occupy tetrahedral voids of the fcc Te substructure. Whereas QENS data probing the picosecond time scale show no significant Lithium Atom mobility in the Q range of 0.08–1.68 A−1, a temperature-dependent change in the elastic scattering term hints at a different time window or a combination of motions with different time scales.