Stress and heat flux via automatic differentiation.

Machine-learning potentials provide computationally efficient and accurate approximations of the Born-Oppenheimer potential energy surface. This potential determines many materials properties and simulation techniques usually require its gradients, in particular forces and stress for molecular dynamics, and heat flux for thermal transport properties. Recently developed potentials feature high body order and can include equivariant semi-local interactions through message-passing mechanisms.

Anharmonicity in Thermal Insulators: An Analysis from First Principles.

The anharmonicity of atomic motion limits the thermal conductivity in crystalline solids. However, a microscopic understanding of the mechanisms active in strong thermal insulators is lacking. In this Letter, we classify 465 experimentally known materials with respect to their anharmonicity and perform fully anharmonic ab initio Green-Kubo calculations for 58 of them, finding 28 thermal insulators with κ<10  W/mK including 6 with ultralow κ≲1  W/mK.

High-pressure synthesis of seven lanthanum hydrides with a significant variability of hydrogen content.

The lanthanum-hydrogen system has attracted significant attention following the report of superconductivity in LaH at near-ambient temperatures and high pressures. Phases other than LaH are suspected to be synthesized based on both powder X-ray diffraction and resistivity data, although they have not yet been identified. Here, we present the results of our single-crystal X-ray diffraction studies on this system, supported by density functional theory calculations, which reveal an unexpected chemical and structural diversity of lanthanum hydrides synthesized in the range of 50 to 180 GPa.

Antimicrobial and cytolytic properties of the frog skin peptide, kassinatuerin-1 and its L- and D-lysine-substituted derivatives.

Kassinatuerin-1, a 21-amino-acid C-terminally alpha-amidated peptide first isolated from the skin of the African frog Kassina senegalensis, adopts an amphipathic alpha-helical conformation in a membrane-mimetic solvent (50% trifluoroethanol) and shows broad-spectrum antimicrobial activity. However, its therapeutic potential is limited by its relatively high cytolytic activity against mammalian cells. The antimicrobial and cytolytic properties of a peptide are determined by an interaction between cationicity, hydrophobicity, alpha-helicity and amphipathicity.

Antimicrobial properties of the frog skin peptide, ranatuerin-1 and its [Lys-8]-substituted analog.

The predicted conformation of ranatuerin-1 (SMLSVLKNLG(10)KVGLGFVACK(20)INK QC), an antimicrobial peptide first isolated from the skin of the bullfrog Rana catesbeiana, comprises three structural domains: alpha-helix (residues 1-8), beta-sheet (residues 11-16) and beta-turn (residues 20-25). Circular dichroism studies confirm significant alpha-helical character in 50% trifluoroethanol. Replacement of Cys-19 and Cys-25 by serine resulted only in decreased antimicrobial potency but deletion of either the cyclic heptapeptide region [residues (19-25)] or the N-terminal domain [residues (1-8)] produced inactive analogs.