We investigate the feasibility of assembling the exceptionally stable isovalent X@Si(16) (X = Ti, Zr and Hf) nanoparticles to form new bulk materials. We use first-principles density functional theory. Our results predict the formation of stable, wide band-gap materials crystallizing in HCP structures in which the cages bind weakly, similar to fullerite. This study suggests new pathways through which endohedral cage clusters may constitute a viable means toward the production of synthetic materials with pre-defined physical and chemical properties.
Replication-competent viruses based on the Edmonston vaccine strain of measles virus (MV-Edm) have potent and selective activities against various types of tumours in vitro but the responses in vivo are more variable. Some tumours are eliminated consistently while others persist despite evidence of ongoing viral propagation. In order to understand these disparate results, we have developed a model for the spatial growth of a tumour population followed by infection with a replicating virus that can spread by cell-to-cell fusion ultimately leading to cell death. We utilize the model to explore both the impact of tumour architecture and the dynamics of tumour cell-virus interactions on the outcome of therapy.
We investigate the vibrational modes and infrared spectra of the exceptionally stable isovalent X @Si 16 ͑X = Ti, Zr, and Hf͒ nanoparticles, making use of first-principles density-functional theory. Our results predict the existence of high-intensity modes of low frequency. An estimate of the electron-phonon coupling strength is also provided based on a single-molecule method introduced recently. The large value of combined with predicted stability of bulk materials assembled with these nanoparticles suggest that these materials, when appropriately doped, may exhibit high-temperature superconducting properties.All ab initio calculations were performed within the generalized gradient approximation 25 to DFT using normconserving pseudopotentials 26 and a plane-wave basis. 27,28 An energy cut-off of 30.0 Hartree ͑816 eV͒ was used throughout, leading to well converged forces within 0.02 eV/ Bohr.
A. Vibrational modesThe vibrational modes of frequency are obtained via a periodic displacement in time of each nuclei IThis leads to the following eigenvalue equation:which involves second derivatives of the ground-state energy E͑R͒ with respect to all N nuclei positions R I ͑I =1, ... ,N͒. Solving these equations leads to a set of frequencies ͑ =0, ... ,3N͒ and corresponding normal modes u = u ,␣ e ␣ involving the collective displacements of the nuclei ͑ =0, ... ,N͒ along the Cartesian directions ͑␣ = x , y , z͒.
B. Infrared spectrumThe absolute infrared intensity of the mode is given by 29
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