Benchmark First-Principles Calculations of Adsorbate Free Energies

ACS Catalysis ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1945-1954 ◽  
Author(s):  
Anshumaan Bajpai ◽  
Prateek Mehta ◽  
Kurt Frey ◽  
Andrew M. Lehmer ◽  
William F. Schneider
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Free Energies

Crystalline and amorphous models of highly damaged Fe

2011 ◽  
Vol 1363 ◽  
Author(s):  
Madhusudan Ojha ◽  
D.M. Nicholson ◽  
Bala. Radhakrishnan ◽  
R. E. Stoller ◽  
Takeshi Egami
Keyword(s):  
Molecular Dynamics ◽  
Structural Characterization ◽  
First Principles ◽  
Glass Phase ◽  
Atomic Level ◽  
First Principles Calculations ◽  
Free Energies ◽  
Cascade Structure ◽  
Dynamics Simulations ◽  
Magnetic States

ABSTRACTThe structure of irradiated material near a primary knock on atom shortly after impact is largely unknown. Molecular dynamics simulations with classical force fields provide the foundation for our current understanding of the resulting cascade. Atomic level structural characterization is often in terms defects within the context of a perfect bulk, however, the choice of the best representation is complicated because the density of defects is high, the material is inhomogeneous and it is not in equilibrium. Here we explore the adaptation of tools typically employed to characterize homogeneous equilibrium liquids to the highly defected region of the cascade. The cascade structure shows some resemblance to that of the liquid or glass phase. The local temperature temporarily exceeds the melting temperature and the free energies of the liquid and defected crystal are comparable. Analysis of cascade structure will be important to the interpretation of first principles calculations of the electronic and magnetic states in cascade structures.

Partial Dislocations under Forward Bias in SiC

2007 ◽  
Vol 556-557 ◽  
pp. 279-282 ◽  
Author(s):  
G. Savini ◽  
A.A. El Barbary ◽  
M.I. Heggie ◽  
Sven Öberg
Keyword(s):  
First Principles ◽  
Dislocation Line ◽  
Forward Bias ◽  
Dislocation Core ◽  
First Principles Calculations ◽  
Dangling Bond ◽  
Free Energies ◽  
Electron Hole ◽  
Partial Dislocations ◽  
Conduction Bands

First-principles calculations are used to investigate the partial dislocations in 4H-SiC. We have shown that the Peierls barriers are strongly dependent on the dislocation core structures. Our results have revealed that the asymmetric reconstruction does not possess midgap states while the symmetric reconstructions, characterized by dangling bond on like atoms along the dislocation line, are always electrically active. We suggested that under forward bias, the free energies of the symmetric reconstructions are dynamically lowered by continuous electron-hole transitions between the respective deep levels and valence/conduction bands.

Electronic Structure and X-ray Absorption Spectra of Rutile TiO2 Using First-Principles Calculations

2014 ◽  
Vol 52 (12) ◽  
pp. 1025-1029
Author(s):  
Min-Wook Oh ◽  
Tae-Gu Kang ◽  
Byungki Ryu ◽  
Ji Eun Lee ◽  
Sung-Jae Joo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Absorption Spectra ◽  
First Principles ◽  
First Principles Calculations ◽  
Rutile Tio2 ◽  
X Ray ◽  
X Ray Absorption

To Bend or Not to Bend, the Dilemma of Multiple Bonds

2019 ◽  
Author(s):  
Michele Pizzocchero ◽  
Matteo Bonfanti ◽  
Rocco Martinazzo
Keyword(s):  
First Principles ◽  
2D Materials ◽  
Main Group ◽  
First Principles Calculations ◽  
Group 14 ◽  
Multiple Bonds ◽  
Main Group Elements ◽  
Structural Distortions

The manuscript addresses the issue of the structural distortions occurring at multiple bonds between high main group elements, focusing on group 14. These distortions are known as trans-bending in silenes, disilenes and higher group analogues, and buckling in 2D materials likes silicene and germanene. A simple but correlated \sigma + \pi model is developed and validated with first-principles calculations, and used to explain the different behaviour of second- and higher- row elements.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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