# Joseph Morrone

Ph.D. in chemistry, Princeton University (2008)

B.S. in chemistry, New York University (2003)

email: jm3267@columbia.edu

webpage: http://www.columbia.edu/~jm3267/res

## Research Interests

I am interested in a wide array of problems, ranging from the diffusion of macromolecules in crowded enviroments to the impact of nuclear quantum effects in hydrogen bonded systems. Recently, we have studied how molecular-scale hydrodynamic interactions impact hydrophobic assembly. Within the framework of Brownian dynamics, we uncovered the interplay between the free energy surface and the frictional force that is engendered by hydrodynamic interactions as two nanoscopic bodies approach each other. The role of large fluctuations and long relaxation times of the solvent confined between two bodies in the kinetics of assmembly has been elucidated by this work. In addition, we have explored the impact of nuclear quantum effects on glass formation. We discovered reentrant behavior in the liqud-glass phase diagram as the magnitude of nuclear quantum effects are increased. Weakly quantum bodies behave as if they have a larger effective radius and therefore exhibit a greater propensity for glass formation. For larger degrees of ''quantumness,'' tunneling and zero motion facilitate movement.

Another focus of my research has been the development and extension of multiple time scale (MTS) molecular dynamics techniques. Multiple time scale techniques facilitate computationally efficient simulation as expensive long range interactions are updated less frequently than more rapidly varying intramolecular forces. This work began with the recognition that there are pitfalls associated with MTS integrators. We discovered that proper conservation of energy depends on carefully designing a suitably smooth function that switches between short-range and long-range interactions. We next developed techniques that alleviate resonance instabilities in MTS integrators. Such instabilities engender a spurious transfer of energy from high frequency to low frequency modes and limit the efficiency of the algorithm. We found that recently developed colored noise thermostats may be designed to correct such instabilities while only minimally perturbing the system's dynamics. In this way, more computationally intensive long-range interactions can be evaluated less frequently, thereby facilitating more efficient simulations.

## Selected Publications

A complete list can be found on my website.

J. A. Morrone, J. Li, and B. J. Berne, ''Interplay between hydrodynamics and the free energy surface in the assembly of nanoscale hydrophobes.'' Journal of Physical Chemistry B, 116, 378 (2012).

L. Lin, J. A. Morrone, R. Car, and M. Parrinello, ''Momentum distribution, vibrational dynamics and the potential of mean force in ice.'' Physical Review B, 83, 220302(R) (2011).

T. E. Markland, J. A. Morrone, B. J. Berne, K. Miyazaki, E. Rabani, and D. R. Reichman, ''Quantum fluctuations can promote or inhibit glass formation.'' Nature Physics, 7, 134 (2011).

J. A. Morrone, T. E. Markland, M. Ceriotti, and B. J. Berne, ''Efficient multiple time scale molecular dynamics: using colored noise thermostats to stabilize resonances.'' Journal of Chemical Physics, 134, 014103 (2011).

J. A. Morrone, R. Zhou, and B. J. Berne, ''Molecular Dynamics with Multiple Time Scales: How to Avoid Pitfalls.'' Journal of Chemical Theory and Computation, 6, 1798 (2010).

J. A. Morrone and R. Car, ''Nuclear quantum effects in water.'' Physical Review Letters, 101, 017801 (2008).