a PhD candidate

at Notre Dame

focused on doing

awesome research.

Take a look.

My day job is as a graduate researcher where I come up with new ways to predict the properties of materials from molecular simulations.

I'm also interested in applied machine learning to discover more efficient ways of carrying out and extracting data from computer simulations.

Molecular mechanics need better software and I love programming, so I contribute to a number of open source projects in my discipline.

When I'm not working I'm usually either rock climbing, doing some outdoor photography, or sometimes both. Oh, and did I mention I'm an amateur chef?

**PhD, University of Notre Dame***Aug 2014 - present*Chemical and Biomolecular Engineering

**MS, University of Notre Dame***Aug 2014 - Jan 2017*Chemical and Biomolecular Engineering

**MS, University of Notre Dame***Aug 2014 - Dec 2016*Applied and Computational Mathematics and Statistics

I've worked on.

- All
- Liquid Crystals
- Thermodynamics

This is my latest (soon to be) published research. For a more complete list check out my CV or Google scholar page link in the footer.

*Hythem Sidky, Alan C. Liddell, Dhagash Mehta, Jonathan D. Hauenstein & Jonathan K. Whitmer*

Industrial & Engineering Chemistry Research, 55(43), 11363–11370 (2016).

Computing the saturation properties from highly accurate Helmholtz equations of state can be challenging for many reasons. The presence of multiple Maxwell loops often results in incorrect solutions to equations defining fluid-phase coexistence. Near the critical point, the same equations also become ill-conditioned. As a consequence, without highly accurate initial guesses, it is difficult to avoid the trivial solution. Here, we propose an algorithm applying the technique of Newton homotopy continuation to determine the coexistence curve for all vapor–liquid equilibrium conditions between the triple and critical points. Importantly, our algorithm is entirely convergence-parameter-free, does not rely on the use of auxiliary equations, requires no initial guesses, and can be used arbitrarily close to the critical point. It is also fully generalizable to arbitrary equations of state, only requiring that they be locally analytic away from the critical point. We demonstrate that the method is capable of handling both technical and reference quality fundamental equations of state, is computationally inexpensive, and is useful in both evaluating individual state points and plotting entire fluid-phase envelopes.

*Hythem Sidky & Jonathan K. Whitmer*

Liquid Crystals, 43(13-15), 2285–2299 (2016).

A free energy perturbation method is used to systematically study the elastic properties of four common Gay–Berne nematogenic models; two with a length-to-diameter ratio κ = 3 [(3, 5, 1, 2) and (3, 5, 1, 3)], a model with κ = 4.4 parameterised for p-terphenyl (4.4, 20, 1, 1), and a discogen with κ = 0.345 (0.345, 0.2, 1, 2). We find the latter two models in particular accurately capture the experimentally measured elastic ratios in apolar achiral systems. The (4.4, 20, 1, 1) model reproduces the elastic constant ratios of p-azoxyanisole remarkably well, and maps to within 30% of the absolute. The (0.345, 0.2, 1, 2) model elastic constants exhibit an unusual temperature dependence similar to recent experimental studies. All models deviate from the mean-field expectation kii ∝ S2. These results represent a crucial first step towards quantitatively accurate coarse-grained liquid crystalline models of self-assembly and response, enabling one to choose a Gay–Berne model based on its measured elastic ratios rather than just its shape and energy anisotropy.

*Hythem Sidky, Dhagash Mehta & Jonathan K. Whitmer*

AIChE Journal, 62(2), 4497–4507 (2016).

The numerical computation of multicomponent mixture critical points has been the subject of much study due to their theoretical and practical importance. Both deterministic and stochastic methods have been applied with varying degrees of reliability and robustness. In this work, we utilize numerical polynomial homotopy continuation (NPHC) to reliably identify all mixture critical points. This method is unique due to its robustness, initialization-free nature and ease of parallelization. For a given system of equations, all complex solutions are found. Computational times are also found to be invariant to mixture composition. We validate this technique against previous work and extend the method to mixtures of up to eight components. NPHC is shown to be a modern and powerful technique which offers mathematical reliability at a moderate computational cost.

*Hythem Sidky & Jonathan K. Whitmer*

Soft Matter, 12(19), 4489–4498 (2016).

Utilizing density-of-states simulations, we perform a full mapping of the phase behavior and elastic responses of binary liquid crystalline mixtures represented by the multicomponent Lebwohl–Lasher model. Our techniques are able to characterize the complete phase diagram, including nematic–nematic phase separation predicted by mean-field theories, but previously not observed in simulations. Mapping this phase diagram permits detailed study of elastic properties across the miscible nematic region. Importantly, we observe for the first time local phase separation and disordering driven by the application of small linear perturbations near the transition temperature and more significantly through nonlinear stresses. These findings are of key importance in systems of blended nematics which contain particulate inclusions, or are otherwise confined.

These are my latest ramblings.

University of Notre Dame

Chemical & Biomolecular Engineering

hsidky@nd.edu