Implementation of a Density Functional Theory-Based Method for the Calculation of the HyperfineA-tensor in Periodic Systems with the Use of Numerical and Slater Type Atomic Orbitals: Application to Paramagnetic Defects

2008 ◽  
Vol 112 (19) ◽  
pp. 4521-4526 ◽  
Author(s):  
Eugene S. Kadantsev ◽  
Tom Ziegler
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Periodic Systems ◽  
Slater Type ◽  
Functional Theory ◽  
Atomic Orbitals

An improved scheme for the calculation of NMR chemical shifts in periodic systems based on gauge including atomic orbitals and density functional theory

2011 ◽  
Vol 89 (9) ◽  
pp. 1150-1161 ◽  
Author(s):  
Dmitry Skachkov ◽  
Mykhaylo Krykunov ◽  
Tom Ziegler
Keyword(s):  
Magnetic Field ◽  
Density Functional Theory ◽  
External Magnetic Field ◽  
Density Functional ◽  
Three Dimensional ◽  
Nuclear Magnetic Moment ◽  
Zero Order ◽  
Periodic Systems ◽  
Functional Theory ◽  
Atomic Orbitals

We report here on an improved first principles method that can determine NMR shielding tensors for periodic systems. Our scheme evaluates the shielding tensor as the second derivative of the total electronic energy with respect to a nuclear magnetic moment and an external magnetic field. Both the induced current density J(α) due to the first perturbation from the nuclear magnetic moment as well as the interaction of J(α) with the second perturbation in the form of an external magnetic field are evaluated analytically. Our approach is based on Kohn–Sham density functional theory and gauge-including atomic orbitals. It employs a Bloch basis set made up of Slater-type or numeric atomic orbitals and represents the Kohn–Sham potential fully without the use of effective core potentials. The method is implemented into the periodic program BAND. The new scheme represents an improvement over a previously proposed method in that use can be made of the zero-order Kohn–Sham orbitals from a calculation based on a primitive cell instead of a supercell. Further, J(α) is evaluated analytically rather than by a finite difference approach. The improvements reduce the required computational time by up to two orders of magnitude for three-dimensional systems. Such a reduction is made possible by the fact that we are using atomic centered basis functions. The new implementation is further able to take into account scalar relativistic effects within the zero-order regular approximation. Results from calculations of NMR shielding constants based on the present approach are presented for systems with one-, two-, and three-dimensional periodicity. The reported values are compared to experiment and results from the previously proposed scheme.

scholarly journals Comparative Analysis of DFTU, ACBN0, and Hybrid Functionals on the Spin Density of YTiO3 and SrRuO3+

2021 ◽  
Vol 11 (2) ◽  
pp. 616
Author(s):  
Francesca Menescardi ◽  
Davide Ceresoli
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Spin Density ◽  
Density Functional ◽  
Functional Theory ◽  
Atomic Orbitals ◽  
Hubbard U ◽  
Density Map ◽  
Hybrid Functionals ◽  
Standard Density

We present a quantitative analysis of the theoretical spin density map of two ferromagnetic perovskites, YTiO3 and SrRuO3. We calculated the spin density using the standard density functional theory (DFT)+U method, where the Hubbard U correction is applied to the Ti and Ru ions, and with the pseudo-hybrid ACBN0 method, where the Hubbard U parameters are determined self-consistently. The ACBN0 calculations yielded a large value of the Hubbard U of the oxygen 2p orbitals. We also used the screened hybrid HSE06 functional, which is widely used to describe the electronic structure of oxides. We used the Quantum Theory of Atoms in Molecules (QTAIM) theory and integrated the spin density in the atomic basins instead of projecting on atomic orbitals. This way, our results can be compared to experimental reports as well as to other DFT calculations.

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