Coarse-grained simulation of transmembrane peptides in the gel phase

We use Dissipative Particle Dynamics simulations, combined with parallel tempering and umbrella sampling, to investigate the potential of mean force between model transmembrane peptides in the various phases of a lipid bilayer, including the low-temperature gel phase. The observed oscillations in the effective interaction between peptides are consistent with the different structures of the surrounding lipid phases

Transition-metal interactions in aluminum-rich intermetallics

The extension of the first-principles generalized pseudopotential theory (GPT) to transition-metal (TM) aluminides produces pair and many-body interactions that allow efficient calculations of total energies. In aluminum-rich systems treated at the pair-potential level, one practical limitation is a transition-metal over-binding that creates an unrealistic TM-TM attraction at short separations in the absence of balancing many-body contributions. Even with this limitation, the GPT pair potentials have been used effectively in total-energy calculations for Al-TM systems with TM atoms at separations greater than 4 AA. An additional potential term may be added for systems with shorter TM atom separations, formally folding repulsive contributions of the three- and higher-body interactions into the pair potentials, resulting in structure-dependent TM-TM potentials. Towards this end, we have performed numerical ab-initio total-energy calculations using VASP (Vienna Ab Initio Simulation Package) for an Al-Co-Ni compound in a particular quasicrystalline approximant structure. The results allow us to fit a short-ranged, many-body correction of the form a(r_0/r)^{b} to the GPT pair potentials for Co-Co, Co-Ni, and Ni-Ni interactions.Comment: 18 pages, 5 figures, submitted to PR

Halide Versus Non‐Halide Salt: Effect of Guanidinium Salts on the Structural, Morphological, and Photovoltaic Performance of Perovskite Solar Cells

We comparatively analyzed the impact of halide and non-halide sources of guanidinium cations, including guanidinium chloride ((NH2)3CCl = GCl) and guanidinium thiocyanate ((NH2)3CSCN = GTC) on the structural, morphological and photophysical properties of (CsMAFA)PbBrxI3-x (x=0.17) (MA= methylammonium, FA= formamidinium)precursor solution does not influence the perovskite structure, however, the formation of photoinactive phases is found to be dependent on the nature of counterion (halide vs non- halide). Furthermore, morphological analysis shows that with the addition of guanidinium salts, the apparent grain size decreases due to the enhancement in nucleation density and/or slow growth of perovskite structures. More importantly, the introduction of GCl led to the fabrication of perovskite solar cells (PSCs) yielding photovoltage as high as 1.16 V (1.1 V for reference). By contrast, the introduction of GTC minimally affected the photovoltage underlining the significance of counterion in improving the photovoltage of PSCs. We also present preliminary results of our DFT based theoretical investigation related to the effect of G cation on the structure of perovskite system. In summary, the insights gained through structural, and morphological characterization helped to understand the critical role of counterions of guanidinium salts in PSCs