The Vibrational Properties of Ultrananocrystalline Diamond Based on Molecular dynamics Simulations

2012 ◽  
Vol 1404 ◽  
Author(s):  
Shashishekar P. Adiga ◽  
Vivekananda P. Adiga ◽  
Robert W. Carpick ◽  
Donald W. Brenner
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Specific Heat ◽  
Molecular Dynamics Simulations ◽  
Vibrational Spectra ◽  
Vibrational Properties ◽  
Ultrananocrystalline Diamond ◽  
Average Grain Size ◽  
Single Crystal Diamond ◽  
Dynamics Simulations

ABSTRACTWe investigate the vibrational properties of ultrananocrystalline diamond (UNCD) using molecular dynamics simulations. We compare the vibrational spectra of two UNCD models of average grain size 2 and 4 nm with single crystal diamond and an isolated nanodiamond (ND) particle. The vibrational spectra of the ND particle and UNCD models exhibit the effect of phonon confinement as well as undercoordinated atoms at the surface/interfaces. This is further reflected in the specific heat of UNCD models and the ND particle that showed enhancements over that of single crystal diamond. The excess specific heat in UNCD models in comparison to single crystal diamond is found to be maximum at approximately 350 K.

Vibrational Properties and Specific Heat of Ultrananocrystalline Diamond: Molecular Dynamics Simulations

2011 ◽  
Vol 115 (44) ◽  
pp. 21691-21699 ◽  
Author(s):  
Shashishekar P. Adiga ◽  
Vivekananda P. Adiga ◽  
Robert W. Carpick ◽  
Donald W. Brenner
Keyword(s):  
Molecular Dynamics ◽  
Specific Heat ◽  
Molecular Dynamics Simulations ◽  
Vibrational Properties ◽  
Ultrananocrystalline Diamond ◽  
Dynamics Simulations

scholarly journals Thermal Properties of Yttrium Aluminum Garnett From Molecular Dynamics Simulations

2011 ◽  
Author(s):  
Majid S. al-Dosari ◽  
D. G. Walker
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Specific Heat ◽  
Molecular Dynamics Simulations ◽  
Yttrium Aluminum Garnet ◽  
System Size ◽  
Yttrium Aluminum ◽  
Dynamics Simulations

Yttrium Aluminum Garnet (YAG, Y3Al5O12) and its varieties have applications in thermographic phosphors, lasing mediums, and thermal barriers. In this work, thermal properties of crystalline YAG where aluminum atoms are substituted with gallium atoms (Y3(Al1−xGax)5O12) are explored with molecular dynamics simulations. For YAG at 300K, the simulations gave values close to experimental values for constant-pressure specific heat, thermal expansion, and bulk thermal conductivity. For various values of x, the simulations predicted no change in thermal expansion, an increase in specific heat, and a decrease in thermal conductivity for x = 50%. Furthermore, the simulations predicted a decrease in thermal conductivity with decreasing system size.

Molecular dynamics simulations of void shrinkage in γ-TiAl single crystal

2015 ◽  
Vol 107 ◽  
pp. 58-65 ◽  
Author(s):  
Xiao-Ting Xu ◽  
Fu-Ling Tang ◽  
Hong-Tao Xue ◽  
Wei-Yuan Yu ◽  
Liang Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Molecular Dynamics Simulations ◽  
Dynamics Simulations

scholarly journals Crystal structure of Ag-exchanged levyne intergrown with erionite: Single-crystal X-ray diffraction and Molecular Dynamics simulations

2020 ◽  
Vol 105 (11) ◽  
pp. 1631-1638 ◽  
Author(s):  
Georgia Cametti ◽  
Sergey V. Churakov
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Molecular Dynamics Simulations ◽  
Exchange Process ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Threefold Axis ◽  
Space Group ◽  
X Ray ◽  
Dynamics Simulations

Abstract The modification of natural zeolites via ion exchange is an efficient technique used to improve their performances and tune their properties for specific applications. In this study, a natural levyne-Ca intergrown with erionite was fully exchanged by Ag+ and its structure [with idealized chemical composition Ag6(Si,Al)18O36·18H2O] was investigated by combining a theoretical and experimental approach. Single-crystal X-ray diffraction data demonstrated that Ag-levyne maintained the R3m space group, characteristic of the natural levyne. Ag ions distribute over partially occupied sites along the threefold axis and, differently from the pristine material, at the wall of the 8-membered ring window of the lev cavity. The lack of ~30% of Ag ions that could not be located by the structural refinement is ascribed to the strong disorder of the extraframework occupants. The structural results obtained by Molecular Dynamics simulations are in overall agreement with the experimental data and showed that, on average, Ag+ is surrounded by ~2 H2O and 1 framework oxygen at distances between 2.43 and 2.6 Å. Molecular Dynamics trajectories indicate that the occurrence of silver inside the D6R cage depends on the water content: silver occupancy of D6R cages is estimated to be 83, 30, and 0% when the structure contains 3, 2.5, and 2 H2O per Ag ion, respectively. The cation-exchange process, as demonstrated by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) spectrometry, affects the intergrown erionite as well. A structural characterization of the Ag-erionite phase (with dimension <100 μm) was possible by means of a CuKα micro-focus source: structure solution pointed to P63/mmc space group, indicating no change with respect to natural erionite. In agreement with previous studies, K ions in the cancrinite cage could not be exchanged, whereas Ag+ is found in the eri cavity.

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