Thermodynamic properties of β-HMX crystal are investigated using the quasi-harmonic approximation and density functional theory within the local density approximation (LDA), generalized gradient approximation (GGA), and GGA + empirical van der Waals (vdW) correction. It is found that GGA well describes the thermal expansion coefficient and heat capacity but fails to produce correct bulk modulus...

The Grouping Genetic Algorithm (GGA) is a Genetic Algorithm heavily modified to suit the structure of grouping problems. Those are the problems where the aim is to find a good partition of a set, or to group together the members of the set. The Bin Packing Problem (BPP) is a well known NP-hard grouping problem items of various sizes have to be grouped inside bins of fixed capacity. On the other...

Surface energies of some simple metals (Be, Al, Mg, Li, and Na) were calculated within density functional theory. Various approximations for the exchange and correlation were tested: local density approximation (LDA), generalized gradient approximations (GGA), and meta–generalized gradient approximation (MGGA). We used the Crystal98 code to calculate slabs with one to 10 layers using both all-e...

The thermal properties of bulk copper are investigated by performing ab initio DFT and DFPT calculations and using the quasiharmonic approximation for the free energy. Using both the LDA and the GGA for the exchangecorrelation potential, we compute the temperature dependence of the lattice constant, coefficient of thermal expansion, bulk modulus, pressure derivative of the bulk modulus, phonon ...

In the present investigation, the results of extensive benchmarking study of density functional theory (DFT) methods on some catalytically important metal dimers have been reported. The calculations were carried out on Al2, Ti2, V2, Cr2, Mn2, Fe2, Co2, Ni2, Cu2, and Zn2 using DFT functionals such as GGA, meta GGA, hybrid meta GGA along with recently developed Minnesota functionals. The bond len...

The local-spin-density approximation and the generalized-gradient approximation ~GGA! are used to perform density-functional total-energy calculations at zero temperature for Fe3Al in the ordered D03 and L12 structures. Our calculations show that commonly used GGA functionals fail to predict the experimentally stable D03 structure as the one with the lower total energy. This qualitative discrep...

This paper describes the development and application of a modified Grouping Genetic Algorithm (GGA) used to identify sets of optimal ambulance locations. The GGA was modified to consider a special case with only two groups, and the reproduction and mutation schemes were modified to operate more efficiently. It was applied to a case study locating ambulances from a fixed set of alternative locat...

The potential energy surface of the Fe dimer is investigated on the basis of density functional theory in the generalized gradient approximation (GGA). Electron correlation effects are taken into account explicitly within the GGA+U approach. We find a value of 2.20 eV for the Coulomb repulsion parameter U to describe the Fe dimer best, yielding a 9 Sigma(g)- ground state with an interatomic sep...

We investigate the electronic and magnetic properties of NiS2, which, by varying the chemical composition substituting S by Se atoms or applying pressure, can be driven across various electronic and magnetic phase transitions. By combining several theoretical methods, we highlight the different role played by the chalcogen dimers and the volume compression in determining the phase transitions, ...

The quasiparticle band structure can be properly described by Hedin's GW approximation (GW), at a high computational cost. For gaps, semilocal density functionals up to the generalized gradient (GGA) level cannot compete with accuracy of hybrid-based approximations or GW. Meta-GGA strong dependence on kinetic energy ingredient potentially give wider gaps compared GGAs. recent TASK meta-GGA func...