TIGHT-BINDING MOLECULAR DYNAMICS STUDY OF C60, C116 AND C120

1996 ◽  
Vol 10 (17) ◽  
pp. 831-838
Author(s):  
ZHILIANG CAO ◽  
XUEPING YU ◽  
JIBING XIANG ◽  
PEIZHU DING ◽  
RUSHAN HAN
Keyword(s):  
Molecular Dynamics ◽  
Molecular Simulation ◽  
Ground State ◽  
Tight Binding ◽  
Ground States ◽  
High Symmetry ◽  
Vibrational Modes ◽  
Relative Movement ◽  
Energy Bands ◽  
Low Symmetry

The geometric structures of C 60, C 116 and C 120 in their ground states are obtained by tight-binding dynamic molecular simulation (TBMD). We find that the ground state of C 60 has high symmetry, Ih, but C 116 and C 120 have low symmetry, D2h. The energy bands and vibrational modes of C 116 and C 120 are complex compared with C 60. Some of them can be easily recognized as C 60 derived and are no longer degenerate but very close, and others are produced by the interaction and relative movement between two C 58 or two C 60.

scholarly journals Local Symmetry Breaking in the High Temperature Regime of SnTe

2014 ◽  
Vol 70 (a1) ◽  
pp. C857-C857
Author(s):  
Kevin Knox ◽  
Emil Bozin ◽  
Christos Malliakas ◽  
Mercouri Kanatzidis ◽  
Simon Billinge
Keyword(s):  
High Temperature ◽  
Ground State ◽  
Ferroelectric Phase ◽  
Local Symmetry ◽  
High Symmetry ◽  
Lead Chalcogenides ◽  
Atomic Pair Distribution Function ◽  
Atomic Pair ◽  
Spatial Fluctuations ◽  
Low Symmetry

The term emphanisis [1] has been coined to define the appearance of local off-centering displacements of ions from a high-symmetry ground state on warming, as recently discovered in PbTe [2]. Such a phenomenon is unusual because, in the canonical view of structural transformations, a low-symmetry ground state evolves into a higher symmetry state on warming. Although it is not uncommon for remnants of a low-symmetry phase to appear as spatial fluctuations at high temperature, the emergence of a locally broken symmetry state from a high symmetry ground state is quite rare. Emphanisis may be behind some long-known, but poorly understood anomalies seen in the lead chalcogenides. However, the origin and nature of emphanisis are still the subject of controversy. Several explanations for emphanisis have been suggested, including a simple response to an underlying anharmonic potential [3], a dynamic ferroelectric-like off-centering [2], and a temperature-dependent competition between ionicity and covalency [1], but an understanding remains elusive. In this talk I will report on atomic pair distribution function (PDF) measurements of the lead-free compound SnTe, which is isostructural to PbTe at high T but with a ferroelectric phase below Tc ~ 100K. Our data show that SnTe also exhibits an emphanitic response, but with an onset temperature well above Tc and a symmetry that is distinct from that of the ferroelectric phase. Taken together these results suggests that the emphanitic and ferroelectric responses are quite distinct.

scholarly journals GROWTH PATTERN OF SILICON CLUSTERS

1995 ◽  
Vol 09 (13) ◽  
pp. 811-816 ◽  
Author(s):  
ATUL BAHEL ◽  
JUN PAN ◽  
MUSHTI V. RAMAKRISHNA
Keyword(s):  
Molecular Dynamics ◽  
Simulated Annealing ◽  
Ground State ◽  
Growth Pattern ◽  
Tight Binding ◽  
Layer Formation ◽  
Silicon Clusters

Tight-binding molecular dynamics simulated annealing technique is employed to search for the ground state geometries of silicon clusters containing 11–17 atoms. These studies revealed that layer formation is the dominant growth pattern in all these clusters. Fullerene-like precursor structures consisting of fused pentagon rings are also observed. The atoms in all these clusters exhibit pronounced preference for residing on the surface.

Prediction of a Very Hard Triclinic Form of Diamond

1995 ◽  
Vol 408 ◽  
Author(s):  
G. Benedek ◽  
M. Facchinetti ◽  
L. Miglio ◽  
S. Serra
Keyword(s):  
Molecular Dynamics ◽  
Ground State ◽  
Tight Binding ◽  
Cubic Phase ◽  
Ground State Structure ◽  
State Structure ◽  
Carbon Structure ◽  
Electronic Density ◽  
Phonon Spectra ◽  
Triclinic Form

AbstractIn a theoretical search for new hypotetical sp3-bonded carbon structure containing five-fold rings as a possible result of fullerene transformation under pressure, we have found a triclinic form of diamond with 16 atoms per unit cell which we called tcl-16. We have calculated the ground state structure, the cohesive energy, the bulk modulus and the electronic density of states by means of tight binding molecular dynamics (TBMD). Finally we have compared the phonon spectra at F to existing Raman data for a non-cubic- phase of diamond.

Ground State Geometries and Vibrational Spectra of Small Hydrogenated Silicon Clusters using Nonorthogonal Tight-Binding Molecular Dynamics

1998 ◽  
Vol 12 (15) ◽  
pp. 1607-1622 ◽  
Author(s):  
Girish R. Gupte ◽  
R. Prasad
Keyword(s):  
Molecular Dynamics ◽  
Vibrational Spectra ◽  
Ground State ◽  
Tight Binding ◽  
Normal Modes ◽  
Silicon Clusters ◽  
Hydrogenated Silicon ◽  
Ground State Structures ◽  
Cohesive Energies ◽  
Homo Lumo

We report a systematic study of ground state structures, vibrational spectra cohesive energies and HOMO-LUMO gaps of small Si n H m clusters (n=1, 2 and m=1–6) and their deuterated derivatives based on the nonorthogonal tight-binding molecular dynamics scheme. The ground state structures have been obtained by using simulated annealing. The bond lengths, bond angles and the frequencies of normal modes are found to be in good agreement with available experimental data and ab initio calculations. Our calculation of cohesive energies indicate SiH 2 to be more stable than SiH 3 or SiH and Si 2 H 4, more stable than Si 2 H 3 or Si 2 H 5.

Molecular Dynamics Study of Commensurate-Incommensurate Phases in Hexamethylenetetramine Suberate

2002 ◽  
Vol 731 ◽  
Author(s):  
Yuansheng Pan ◽  
David Brown ◽  
Gervais Chapuis
Keyword(s):  
Molecular Dynamics ◽  
Dynamics Simulation ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Incommensurate Structure ◽  
Incommensurate Modulation ◽  
Long Range Ordering ◽  
Lock In ◽  
Low Symmetry

AbstractIncommensurate structure of Hexamethylenetetramine suberate (C6H12N4)(HOOC-(CH2)6-COOH) has been solved from single crystal x-ray diffraction data. A molecular dynamics simulation of this system was carried out from 15 K to 580K. A second-generation consistent forcefield (CFF) and a compensating pressure tensor field were used to describe the interactions between atoms and to account for deficiencies in the forcefield. Starting from the experimental 298K structure, the phase transitions were investigated over an extended temperature range. A high symmetry commensurate structure exists at temperatures between 410K and 290K. For temperatures lower than 290K, a new periodicity appears in the structure. The system reaches a low symmetry lock-in phase at about 150K. An incommensurate structure appears between the high and low symmetry phases between 290K and 150K. The new periodicity associated with the incommensurate modulation is due to the appearance of additional long range ordering of the carbon chains. The present simulation not only reproduces well the experimental x-ray diffraction results but also gives new insight into the origin of the incommensurate behavior.

The usefulness of high index low symmetry zone axes for holz line analysis

1987 ◽  
Vol 45 ◽  
pp. 384-385
Author(s):  
C. M. Sung ◽  
D. B. Williams
Keyword(s):  
Lattice Parameter ◽  
High Order ◽  
Zone Axis ◽  
High Index ◽  
High Symmetry ◽  
Second Phases ◽  
Line Patterns ◽  
Low Symmetry ◽  
Line Analysis

Researchers have tended to use high symmetry zone axes (e.g. <111> <114>) for High Order Laue Zone (HOLZ) line analysis since Jones et al reported the origin of HOLZ lines and described some of their applications. But it is not always easy to find HOLZ lines from a specific high symmetry zone axis during microscope operation, especially from second phases on a scale of tens of nanometers. Therefore it would be very convenient if we can use HOLZ lines from low symmetry zone axes and simulate these patterns in order to measure lattice parameter changes through HOLZ line shifts. HOLZ patterns of high index low symmetry zone axes are shown in Fig. 1, which were obtained from pure Al at -186°C using a double tilt cooling holder. Their corresponding simulated HOLZ line patterns are shown along with ten other low symmetry orientations in Fig. 2. The simulations were based upon kinematical diffraction conditions.

scholarly journals Insight into the origin of SARS-CoV-2 through structural analysis of receptor recognition: a molecular simulation study

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8718-8729
Author(s):  
Jixue Sun ◽  
Meijiang Liu ◽  
Na Yang
Keyword(s):  
Molecular Dynamics ◽  
Structural Analysis ◽  
Molecular Dynamics Simulations ◽  
Molecular Simulation ◽  
Simulation Study ◽  
Receptor Recognition ◽  
Dynamics Simulations ◽  
Insight Into

The origin of SARS-CoV-2 through structural analysis of receptor recognition was investigated by molecular dynamics simulations.

Mechanistic analysis of light-driven overcrowded alkene-based molecular motors by multiscale molecular simulations

2021 ◽  
Vol 23 (14) ◽  
pp. 8525-8540
Author(s):  
Mudong Feng ◽  
Michael K. Gilson
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Molecular Dynamics Simulations ◽  
Ground State ◽  
Molecular Motors ◽  
Motor Performance ◽  
Molecular Simulations ◽  
Mechanistic Analysis ◽  
Dynamics Simulations ◽  
Shed Light

Ground-state and excited-state molecular dynamics simulations shed light on the rotation mechanism of small, light-driven molecular motors and predict motor performance. How fast can they rotate; how much torque and power can they generate?

Impact of vibronic coupling effects on light-driven charge transfer in pyrene-functionalized middle and large-sized Metalloid Gold Nanoclusters from Ehrenfest dynamics.

2021 ◽  
Author(s):  
Adrian Dominguez-Castro ◽  
Thomas Frauenheim
Keyword(s):  
Molecular Dynamics ◽  
Charge Transfer ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Gold Nanoclusters ◽  
Tight Binding ◽  
Time Dependent ◽  
Effective Strategy ◽  
Dynamics Simulations ◽  
Dependent Density

Theoretical calculations are an effective strategy to comple- ment and understand experimental results in atomistic detail. Ehrenfest molecular dynamics simulations based on the real-time time-dependent density functional tight-binding (RT-TDDFTB) approach...

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