Using density functional theory calculations and ab initio molecular dynamics simulations, we have observed a clear evidence of Li₂S₄ → Li₂S₂ transition by studying systematic changes in the simulated Raman spectra of (Li₂S₄)_n, n = 1, 4, and 8, towards that of (Li₂S₂)₈.

We investigate the structure and electronic properties of phosphatidylcholine (PC) under different degrees of hydration at the single-molecule and monolayer type level by linear scaling ab initio calculations. Upon hydration, the phospholipid undergoes drastic long-range conformational rearrangements which lead to a sickle-like ground-state shape. The structural unit of the tilted gel-phase PC appears to be a water-bridged PC dimer. We find that hydration dramatically alters the surface potential, dipole and quadrupole moments of the lipids and consequently guides the interactions of the lipids with other molecules and the communication between cells.

It has been argued that the electron-hole puddles formed on graphene are mostly due to substrate-induced charged impurities [J. Martin et al., Nature Phys. 4, 144 (2008), Y. Zhang et al., Nature Phys. 5, 722 (2009)]. Here, using first-principles ab initio calculations, we show that the existence of ripples and electron-hole puddles is indeed an intrinsic property of graphene at finite temperatures. We found a relatively large correlation between the electronic charge density distribution on the surface of graphene and its local geometrical properties, such as local mean curvature and average bond length. We show that the electron and hole puddles appear in places where curvatures are large and small, respectively. We also determined the average sizes of the observed electron-hole puddles and have reported their percolating nature. DOI: http://dx.doi.org/10.1103/PhysRevB.83.165434 ©2011 American Physical Society