Comment on ‘Nanoscale water capillary bridges under deeply negative pressure’ [Chem. Phys. Lett. 451 (2008) 88]

Yang et al. reported pull-off force measurements between an atomic force microscope tip and a silicon wafer. They deduced the pressure of liquid water inside the capillary bridge formed in humid air. They claimed that their ‘research shows that nanoscale water capillary bridges are metastable and have absolutely negative pressure approaching the limit of stability for water’ (around −200 MPa at room temperature). Indeed, pressures reaching −160 MPa were reported, establishing a world record. However, we show that the bridges are not metastable, that the analysis used suffers from internal inconsistency, and that several assumptions made are questionable.     

Comment on "Quasirelativistic theory equivalent to fully relativistic theory" [J. Chem. Phys. 123, 241102 (2005)

The connection between the exact quasirelativistic approach developed in the title reference [W. Kutzelnigg and W. Liu, J. Chem. Phys. 123, 241102 (2005)] and the method of elimination of the small component in matrix form developed previously by Dyall is explicitly worked out. An equation that links Hermitian and non-Hermitian formulations of the exact quasirelativistic theory is derived. Besides establishing a kinship between the existing formulations, the proposed equation can be employed for the derivation of new formulations of the exact quasirelativistic theory.     

Comment on "anharmonic properties of the vibrational quantum computer" [J. Chem. Phys. 126, 204102 (2007)

Suitable molecules for quantum computing cannot be discussed in terms of anharmonicity and CNOT gates alone. The validity of the approximate approach [M. Zhao and D. Babikov, J. Chem. Phys.126, 204102 (2007)] is limited. Frequencies and anharmonicities cannot be used independent from the molecule. Hermite polynomials with the linear approximation for the dipole moment lead to oversimplified gates with potentially low intensities.     

Comment on "Comment on 'Constant temperature molecular dynamics simulations by means of a stochastic collision model. II. The harmonic oscillator' [J. Chem. Phys. 104, 3732 (1996)]" [J. Chem. Phys. 106, 1646 (1997)

An argument brought forward by Sholl and Fichthorn against the stochastic collision-based constant temperature algorithm for molecular dynamics simulations developed by Kast et al. is refuted. It is demonstrated that the large temperature fluctuations noted by Sholl and Fichthorn are due to improperly chosen initial conditions within their formulation of the algorithm. With the original form or by suitable initialization of their variant no deficient behavior is observed.