The Experts below are selected from a list of 70383 Experts worldwide ranked by ideXlab platform
Jurgen Gauss - One of the best experts on this subject based on the ideXlab platform.
-
accurate prediction of hyperfine coupling tensors for main group elements using a unitary group based rigorously Spin adapted coupled cluster theory
2019Co-Authors: Dipayan Datta, Jurgen GaussAbstract:We present the development of a perturbative triples correction scheme for the previously reported unitary group based Spin-adapted combinatoric open-shell coupled-cluster (CC) singles and doubles (COS-CCSD) approach and report on the applications of the newly developed method, termed “COS-CCSD(T)”, to the calculation of hyperfine coupling (HFC) tensors for radicals consisting of hydrogen, second- and third-row elements. The COS-CCSD(T) method involves a single noniterative step with N7 scaling of the computational cost for the calculation of triples corrections to the energy. The key feature of this development is the use of spatial semicanonical orbitals generated from standard restricted open-shell Hartree–Fock (ROHF) orbitals, which allows the unperturbed Hamiltonian operator to be defined in terms of a diagonal Spin-free Fock operator. The HFC tensors are computed as a first-order property via implementation of an analytic derivative scheme. The required one-Particle Spin density matrix is computed b...
-
benchmark coupled cluster g tensor calculations with full inclusion of the two Particle Spin orbit contributions
2017Co-Authors: Ajith Perera, Jurgen Gauss, Prakash Verma, Jorge A MoralesAbstract:We present a parallel implementation to compute electron Spin resonance g-tensors at the coupled-cluster singles and doubles (CCSD) level which employs the ACES III domain-specific software tools for scalable parallel programming, i.e., the super instruction architecture language and processor (SIAL and SIP), respectively. A unique feature of the present implementation is the exact (not approximated) inclusion of the five one- and two-Particle contributions to the g-tensor [i.e., the mass correction, one- and two-Particle paramagnetic Spin-orbit, and one- and two-Particle diamagnetic Spin-orbit terms]. Like in a previous implementation with effective one-electron operators [J. Gauss et al., J. Phys. Chem. A 113, 11541–11549 (2009)], our implementation utilizes analytic CC second derivatives and, therefore, classifies as a true CC linear-response treatment. Therefore, our implementation can unambiguously appraise the accuracy of less costly effective one-Particle schemes and provide a rationale for their w...
-
communication Spin densities within a unitary group based Spin adapted open shell coupled cluster theory analytic evaluation of isotropic hyperfine coupling constants for the combinatoric open shell coupled cluster scheme
2015Co-Authors: Dipayan Datta, Jurgen GaussAbstract:We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a Spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-Particle Spin-density matrix required in these calculations is outlined within the Spin-free formulation of the COSCC approach. In this scheme, the one-Particle Spin-density matrix for an open-shell state with Spin S and MS = + S is expressed in terms of the one- and two-Particle Spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH2CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.
Dipayan Datta - One of the best experts on this subject based on the ideXlab platform.
-
accurate prediction of hyperfine coupling tensors for main group elements using a unitary group based rigorously Spin adapted coupled cluster theory
2019Co-Authors: Dipayan Datta, Jurgen GaussAbstract:We present the development of a perturbative triples correction scheme for the previously reported unitary group based Spin-adapted combinatoric open-shell coupled-cluster (CC) singles and doubles (COS-CCSD) approach and report on the applications of the newly developed method, termed “COS-CCSD(T)”, to the calculation of hyperfine coupling (HFC) tensors for radicals consisting of hydrogen, second- and third-row elements. The COS-CCSD(T) method involves a single noniterative step with N7 scaling of the computational cost for the calculation of triples corrections to the energy. The key feature of this development is the use of spatial semicanonical orbitals generated from standard restricted open-shell Hartree–Fock (ROHF) orbitals, which allows the unperturbed Hamiltonian operator to be defined in terms of a diagonal Spin-free Fock operator. The HFC tensors are computed as a first-order property via implementation of an analytic derivative scheme. The required one-Particle Spin density matrix is computed b...
-
communication Spin densities within a unitary group based Spin adapted open shell coupled cluster theory analytic evaluation of isotropic hyperfine coupling constants for the combinatoric open shell coupled cluster scheme
2015Co-Authors: Dipayan Datta, Jurgen GaussAbstract:We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a Spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-Particle Spin-density matrix required in these calculations is outlined within the Spin-free formulation of the COSCC approach. In this scheme, the one-Particle Spin-density matrix for an open-shell state with Spin S and MS = + S is expressed in terms of the one- and two-Particle Spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH2CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.
G S Bisnovatyikogan - One of the best experts on this subject based on the ideXlab platform.
-
parameters of innermost stable circular orbits of Spinning test Particles numerical and analytical calculations
2016Co-Authors: Yu O Tsupko, G S Bisnovatyikogan, Paul I JefremovAbstract:The motion of classical Spinning test Particles in the equatorial plane of a Kerr black hole is considered for the case where the Particle Spin is perpendicular to the equatorial plane.We review some results of our recent research of the innermost stable circular orbits (ISCO) [1] and present some new calculations. The ISCO radius, total angular momentum, energy, and orbital angular frequency are considered. We calculate the ISCO parameters numerically for different values of the Kerr parameter a and investigate their dependence on both black hole and test Particle Spins. Then we describe in detail how to calculate analytically small-Spin corrections to the ISCO parameters for an arbitrary values of a. The cases of Schwarzschild, slowly rotating Kerr and extreme Kerr black holes are considered. The use of the orbital angular momentum is discussed. We also consider the ISCO binding energy. It is shown that the efficiency of accretion onto an extreme Kerr black hole can be larger than the maximum known efficiency (42%) if the test body has a Spin.
-
parameters of innermost stable circular orbits of Spinning test Particles numerical and analytical calculations
2016Co-Authors: Yu O Tsupko, G S Bisnovatyikogan, Paul I JefremovAbstract:The motion of classical Spinning test Particles in the equatorial plane of a Kerr black hole is considered for the case where the Particle Spin is perpendicular to the equatorial plane. We review some results of our recent research of the innermost stable circular orbits (ISCO) [P.I. Jefremov, this http URL. Tsupko and G.S. Bisnovatyi-Kogan, Phys.Rev. D 91 124030 (2015)] and present some new calculations. The ISCO radius, total angular momentum, energy, and orbital angular frequency are considered. We calculate the ISCO parameters numerically for different values of the Kerr parameter $a$ and investigate their dependence on both black hole and test Particle Spins. Then we describe in details how to calculate analytically small-Spin corrections to the ISCO parameters for an arbitrary values of $a$. The cases of Schwarzschild, slowly rotating Kerr and extreme Kerr black hole are considered. The use of the orbital angular momentum is discussed. We also consider the ISCO binding energy. It is shown that the efficiency of accretion onto an extreme Kerr black hole can be larger than the maximum known efficiency (42 %) if the test body has a Spin.
-
innermost stable circular orbits of Spinning test Particles in schwarzschild and kerr space times
2015Co-Authors: Paul I Jefremov, Oleg Yu Tsupko, G S BisnovatyikoganAbstract:We consider the motion of classical Spinning test Particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-Spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of Spinning test Particles in the case of vectors of black hole Spin, Particle Spin and orbital angular momentum being collinear to each other. We analytically derive the small-Spin linear corrections for arbitrary Kerr parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in detail. For a slowly rotating black hole, the ISCO parameters are obtained up to quadratic in $a$ and Particle's Spin $s$ terms. From the formulas obtained it is seen that the Spin-orbital coupling has attractive character when Spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating Particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary Spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the Particle's Spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-Spin linear corrections for the total angular momentum, energy and frequency at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary $a$ and $s$ is also explicitly written.
-
innermost stable circular orbits of Spinning test Particles in schwarzschild and kerr space times
2015Co-Authors: Paul I Jefremov, Oleg Yu Tsupko, G S BisnovatyikoganAbstract:We consider the motion of classical Spinning test Particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-Spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of Spinning test Particles in the case of vectors of black hole Spin, Particle Spin and orbital angular momentum being collinear to each other. We analytically derive the small-Spin linear corrections for arbitrary Kerr parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in details. For a slowly rotating black hole the ISCO parameters are obtained up to quadratic in $a$ and Particle's Spin $s$ terms. From the formulae obtained it is seen that the Spin-orbital coupling has attractive character when Spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating Particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary Spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the Particle's Spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-Spin linear corrections for the total angular momentum and energy at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary $a$ and $s$ is also explicitly written.
Paul I Jefremov - One of the best experts on this subject based on the ideXlab platform.
-
parameters of innermost stable circular orbits of Spinning test Particles numerical and analytical calculations
2016Co-Authors: Yu O Tsupko, G S Bisnovatyikogan, Paul I JefremovAbstract:The motion of classical Spinning test Particles in the equatorial plane of a Kerr black hole is considered for the case where the Particle Spin is perpendicular to the equatorial plane.We review some results of our recent research of the innermost stable circular orbits (ISCO) [1] and present some new calculations. The ISCO radius, total angular momentum, energy, and orbital angular frequency are considered. We calculate the ISCO parameters numerically for different values of the Kerr parameter a and investigate their dependence on both black hole and test Particle Spins. Then we describe in detail how to calculate analytically small-Spin corrections to the ISCO parameters for an arbitrary values of a. The cases of Schwarzschild, slowly rotating Kerr and extreme Kerr black holes are considered. The use of the orbital angular momentum is discussed. We also consider the ISCO binding energy. It is shown that the efficiency of accretion onto an extreme Kerr black hole can be larger than the maximum known efficiency (42%) if the test body has a Spin.
-
parameters of innermost stable circular orbits of Spinning test Particles numerical and analytical calculations
2016Co-Authors: Yu O Tsupko, G S Bisnovatyikogan, Paul I JefremovAbstract:The motion of classical Spinning test Particles in the equatorial plane of a Kerr black hole is considered for the case where the Particle Spin is perpendicular to the equatorial plane. We review some results of our recent research of the innermost stable circular orbits (ISCO) [P.I. Jefremov, this http URL. Tsupko and G.S. Bisnovatyi-Kogan, Phys.Rev. D 91 124030 (2015)] and present some new calculations. The ISCO radius, total angular momentum, energy, and orbital angular frequency are considered. We calculate the ISCO parameters numerically for different values of the Kerr parameter $a$ and investigate their dependence on both black hole and test Particle Spins. Then we describe in details how to calculate analytically small-Spin corrections to the ISCO parameters for an arbitrary values of $a$. The cases of Schwarzschild, slowly rotating Kerr and extreme Kerr black hole are considered. The use of the orbital angular momentum is discussed. We also consider the ISCO binding energy. It is shown that the efficiency of accretion onto an extreme Kerr black hole can be larger than the maximum known efficiency (42 %) if the test body has a Spin.
-
innermost stable circular orbits of Spinning test Particles in schwarzschild and kerr space times
2015Co-Authors: Paul I Jefremov, Oleg Yu Tsupko, G S BisnovatyikoganAbstract:We consider the motion of classical Spinning test Particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-Spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of Spinning test Particles in the case of vectors of black hole Spin, Particle Spin and orbital angular momentum being collinear to each other. We analytically derive the small-Spin linear corrections for arbitrary Kerr parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in detail. For a slowly rotating black hole, the ISCO parameters are obtained up to quadratic in $a$ and Particle's Spin $s$ terms. From the formulas obtained it is seen that the Spin-orbital coupling has attractive character when Spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating Particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary Spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the Particle's Spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-Spin linear corrections for the total angular momentum, energy and frequency at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary $a$ and $s$ is also explicitly written.
-
innermost stable circular orbits of Spinning test Particles in schwarzschild and kerr space times
2015Co-Authors: Paul I Jefremov, Oleg Yu Tsupko, G S BisnovatyikoganAbstract:We consider the motion of classical Spinning test Particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-Spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of Spinning test Particles in the case of vectors of black hole Spin, Particle Spin and orbital angular momentum being collinear to each other. We analytically derive the small-Spin linear corrections for arbitrary Kerr parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in details. For a slowly rotating black hole the ISCO parameters are obtained up to quadratic in $a$ and Particle's Spin $s$ terms. From the formulae obtained it is seen that the Spin-orbital coupling has attractive character when Spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating Particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary Spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the Particle's Spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-Spin linear corrections for the total angular momentum and energy at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary $a$ and $s$ is also explicitly written.
Chan, Garnet Kin-lic - One of the best experts on this subject based on the ideXlab platform.
-
Ab Initio Full Cell GW+DMFT for Correlated Materials
2020Co-Authors: Zhu Tianyu, Chan, Garnet Kin-licAbstract:Quantitative prediction of electronic properties in correlated materials requires simulations without empirical truncations and parameters. We present a method to achieve this goal through a new ab initio formulation of dynamical mean-field theory (DMFT). Instead of using small impurities defined in a low-energy subspace, which require complicated downfolded interactions which are often approximated, we describe a full cell $GW$+DMFT approach, where the impurities comprise all atoms in a unit cell or supercell of the crystal. Our formulation results in large impurity problems, which we treat here using an efficient coupled-cluster impurity solver that works on the real-frequency axis, combined with a one-shot $G_0W_0$ treatment of long-range interactions. We apply our full cell approach to bulk Si and two antiferromagnetic correlated insulators, NiO and $\alpha$-Fe$_2$O$_3$, with impurities containing up to 10 atoms and 124 orbitals. We find that spectral properties, magnetic moments, and two-Particle Spin correlation functions are obtained in good agreement with experiments. In addition, in the metal oxides, the balanced treatment of correlations involving all orbitals in the cell leads to new insights into the orbital character around the insulating gap.Comment: 7 pages, 5 figure
-
Ab Initio Full Cell GW+DMFT for Correlated Materials
2020Co-Authors: Zhu Tianyu, Chan, Garnet Kin-licAbstract:Quantitative prediction of electronic properties in correlated materials requires simulations without empirical truncations and parameters. We present a method to achieve this goal through a new ab initio formulation of dynamical mean-field theory (DMFT). Instead of using small impurities defined in a low-energy subspace, which require complicated downfolded interactions which are often approximated, we describe a full cell GW+DMFT approach, where the impurities comprise all atoms in a unit cell or supercell of the crystal. Our formulation results in large impurity problems, which we treat here using an efficient coupled-cluster impurity solver that works on the real-frequency axis, combined with a one-shot G0W0 treatment of long-range interactions. We apply our full cell approach to bulk Si and two antiferromagnetic correlated insulators, NiO and α-Fe₂O₃, with impurities containing up to 10 atoms and 124 orbitals. We find that spectral properties, magnetic moments, and two-Particle Spin correlation functions are obtained in good agreement with experiments. In addition, in the metal oxides, the balanced treatment of correlations involving all orbitals in the cell leads to new insights into the orbital character around the insulating gap