A new phase in the decomposition of Mg(BH4)2: first-principles simulated annealing

2009 ◽  
Vol 19 (38) ◽  
pp. 7081 ◽  
Author(s):  
M. J. van Setten ◽  
W. Lohstroh ◽  
M. Fichtner
Keyword(s):  
Simulated Annealing ◽  
First Principles ◽  
New Phase

scholarly journals A New Phase of GaN

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Qingyang Fan ◽  
Changchun Chai ◽  
Qun Wei ◽  
Jionghao Yang ◽  
Peikun Zhou ◽  
...  
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Ambient Pressure ◽  
Young Modulus ◽  
Structure Study ◽  
First Principles Calculations ◽  
Hydrogen Storage Material ◽  
Storage Material ◽  
New Phase

The structural, mechanical, and electronic properties of the orthorhombic GaN (Pnma-GaN) are investigated at ambient pressure by using first-principles calculations method with the ultrasoft pseudopotential scheme. The elastic constants and phonon calculations reveal Pnma-GaN is mechanically and dynamically stable at ambient pressure. The calculated Young modulus of Pnma-GaN is 170 GPa, which is the three-fifths of wurtzite-GaN. Electronic structure study shows that Pnma-GaN is a direct semiconductor with band gap of 1.847 eV. The anisotropic calculation shows that wurtzite-GaN has a smaller elastic anisotropy than that of Pnma-GaN in Young’s modulus. In addition, when the composition of aluminum increases from 0 to 0.063 in the alloy, the band gap decreases initially and increases afterward for Pnma-Ga1−xAlxN, while, for wurtzite-Ga1−xAlxN, the band gap increases with the increasing compositionx. Due to the structural porous feature, Pnma-GaN can also be expected to be a good hydrogen storage material.

A new phase of lithiated titania predicted from first principles

2003 ◽  
Vol 371 (1-2) ◽  
pp. 150-156 ◽  
Author(s):  
Marina V. Koudriachova ◽  
Simon W. de Leeuw ◽  
Nicholas M. Harrison
Keyword(s):  
First Principles ◽  
New Phase

Lowest-energy structures of cationic P2m+1+ (m=1–12) clusters from first-principles simulated annealing

2010 ◽  
Vol 485 (1-3) ◽  
pp. 26-30 ◽  
Author(s):  
Tao Xue ◽  
Jing Luo ◽  
Si Shen ◽  
Fengyu Li ◽  
Jijun Zhao
Keyword(s):  
Simulated Annealing ◽  
First Principles

Simulated annealing structure solution of a new phase of dicalcium silicate Ca2SiO4 and the mechanism of structural changes from α-dicalcium silicate hydrate to αL′-dicalcium silicate via the new phase

2002 ◽  
Vol 58 (4) ◽  
pp. 613-621 ◽  
Author(s):  
H. Toraya ◽  
S. Yamazaki
Keyword(s):  
Simulated Annealing ◽  
Structural Changes ◽  
Rietveld Method ◽  
Three Dimensional ◽  
Structural Type ◽  
Dicalcium Silicate ◽  
Coordination Sites ◽  
Structure Solution ◽  
Increasing Temperature ◽  
New Phase

A new phase of dicalcium silicate (Ca2SiO4) was formed by heating α-dicalcium silicate hydrate [α-Ca2(SiO4H)OH = α-C2SH] at temperatures of ∼663–763 K, and it was transformed into \alpha _{\rm L} ^\prime-Ca2SiO4 (= \alpha _{\rm L} ^\prime-C2S) above ∼1193 K. The crystal structure of the new phase (hereafter called x-C2S) has been determined by simulated annealing and refined by the Rietveld method using synchrotron radiation powder diffraction data. The structure consists of isolated SiO4 tetrahedra and a three-dimensional CaO n polyhedral network, forming a new structural type of dicalcium silicate. A structural change from α-C2SH to x-C2S is compelled by large displacements of SiO4 tetrahedra, accompanied by dehydration, in the direction perpendicular to the two-dimensional Ca(O,OH) n polyhedral network in α-C2SH. With increasing temperature, sizes of CaO n polyhedra in x-C2S become too large to confine Ca atoms at the sixfold to eightfold coordination sites. Then the structure of x-C2S is transformed into \alpha _{\rm L} ^\prime-C2S, having eightfold to tenfold coordination sites for the Ca atoms.

DETERMINATION OF THE GROUND-STATE GEOMETRIES OF COPPER CLUSTERS BY SIMULATED ANNEALING WITHIN AN EQUIVALENT CRYSTAL APPROACH

2003 ◽  
Vol 17 (03) ◽  
pp. 273-279
Author(s):  
AMITAVA BANERJEA ◽  
RADHIKA PROSAD DATTA ◽  
ABHIJIT MOOKERJEE ◽  
A. K. BHATTACHARYYA
Keyword(s):  
Simulated Annealing ◽  
First Principles ◽  
Monte Carlo Algorithm ◽  
Equilibrium Geometry ◽  
Efficient Tool ◽  
Copper Clusters ◽  
Atom Clusters ◽  
Metropolis Monte Carlo ◽  
Semi Empirical

We determine the lowest energy structures of small (11–20 atoms) copper clusters. The semi-empirical Equivalent Crystal Theory (ECT) is used in conjunction with the Metropolis Monte Carlo algorithm to determine the equilibrium geometry of each cluster via simulated annealing. The optimum structures of the clusters in this size range are found to be derived from icosahedral structures. The 13-atom cluster is an icosahedron and the 19-atom is a double-icosahedron. The other sizes show structures related to these. The 11-atom clusters, however, show somewhat different structures. We propose the ECT as an efficient tool for developing starting structures for more chemically accurate, first principles and therefore computationally very demanding, approaches.

Determination of Total Energy Tight Binding Parameters from First Principles Calculations Using Adaptive Simulated Annealing

2001 ◽  
Vol 700 ◽  
Author(s):  
Anders G. Froseth ◽  
Peter Derlet ◽  
Ragnvald Hoier
Keyword(s):  
Simulated Annealing ◽  
Total Energy ◽  
First Principles ◽  
Linear Optimization ◽  
Tight Binding ◽  
Accurate Method ◽  
Optimization Method ◽  
Binding Parameters ◽  
Non Linear

AbstractEmpirical Total Energy Tight Binding (TETB) has proven to be a fast and accurate method for calculating materials properties for various system, including bulk, surface and amorphous structures. The determination of the tight binding parameters from first-principles results is a multivariate, non-linear optimization problem with multiple local minima. Simulated annealing is an optimization method which is flexible and “guaranteed” to find a global minimum, opposed to classical methods like non-linear least squares algorithms. As an example results are presented for a nonorthogonal s,p parameterization for Silicon based on the NRL tight binding formalism.

A new phase of the two-dimensional ReS2 sheet with tunable magnetism

2018 ◽  
Vol 6 (5) ◽  
pp. 1248-1254 ◽  
Author(s):  
Zhongti Sun ◽  
Haifeng Lv ◽  
Zhiwen Zhuo ◽  
Abdul Jalil ◽  
Wenhua Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
New Phase

A new trimer phase of 2D ReS2 with tunable magnetism is reported by using first-principles calculations.

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