7 research outputs found
Fashion design in a multicultural space
The collective monograph contains the results of the synthesis of theoretical materials, as well as the authors` applied research developments on the design of the clothes of different assortment and purpose, made from different materials considering the modern scientific methods
DFTB+, a software package for efficient approximate density functional theory based atomistic simulations
DFTB+ is a versatile community developed open source software package offering fast and efficient methods for carrying out atomistic quantum mechanical simulations. By implementing various methods approximating density functional theory (DFT), such as the density functional based tight binding (DFTB) and the extended tight binding method, it enables simulations of large systems and long timescales with reasonable accuracy while being considerably faster for typical simulations than the respective ab initio methods. Based on the DFTB framework, it additionally offers approximated versions of various DFT extensions including hybrid functionals, time dependent formalism for treating excited systems, electron transport using non-equilibrium Green's functions, and many more. DFTB+ can be used as a user-friendly standalone application in addition to being embedded into other software packages as a library or acting as a calculation-server accessed by socket communication. We give an overview of the recently developed capabilities of the DFTB+ code, demonstrating with a few use case examples, discuss the strengths and weaknesses of the various features, and also discuss on-going developments and possible future perspectives
Extensions of the Time-Dependent Density Functional Based Tight-Binding Approach
The time-dependent
density functional based tight-binding (TD-DFTB)
approach is generalized to account for fractional occupations. In
addition, an on-site correction leads to marked qualitative and quantitative
improvements over the original method. Especially, the known failure
of TD-DFTB for the description of Ï â Ï* and <i>n</i> â Ï* excitations is overcome. Benchmark calculations
on a large set of organic molecules also indicate a better description
of triplet states. The accuracy of the revised TD-DFTB method is found
to be similar to first principles TD-DFT calculations at a highly
reduced computational cost. As a side issue, we also discuss the generalization
of the TD-DFTB method to spin-polarized systems. In contrast to an
earlier study, we obtain a formalism that is fully consistent with
the use of local exchange-correlation functionals in the ground state
DFTB method
Extensions of the time-dependent density functional based tight-binding approach
The time-dependent density functional based tight-binding (TD-DFTB) approach
is generalized to account for fractional occupations. In addition, an on-site
correction leads to marked qualitative and quantitative improvements over the
original method. Especially, the known failure of TD-DFTB for the description
of \sigma -> \pi* and n -> \pi* excitations is overcome. Benchmark calculations
on a large set of organic molecules also indicate a better description of
triplet states. The accuracy of the revised TD-DFTB method is found to be
similar to first principles TD-DFT calculations at a highly reduced
computational cost. As a side issue, we also discuss the generalization of the
TD-DFTB method to spin-polarized systems. In contrast to an earlier study
[Trani et al., JCTC 7 3304 (2011)], we obtain a formalism that is fully
consistent with the use of local exchange-correlation functionals in the ground
state DFTB method