Advanced Simulation Methods SS 2016
- Lecture and Tutorials (2 SWS in total)
- Prof. Dr. Christian Holm, Dr. Jens Smiatek, JP. Dr. Maria Fyta
- Course language
- English or German
- ICP, Allmandring 3; Room: tba.
The course will consist of four modules supervised by Prof. Dr. Christian Holm, Dr. Jens Smiatek, JP. Dr. Maria Fyta that contain exercises, presentations, discussion meetings, and written reports, worked out in groups of up to four people.
A preliminary registration for this course is mandatory. Interested students write an Email to Maria Fyta
Module 4: Maria Fyta, Frank Uhlig, Inter-atomic interactions modeled with quantum mechanical simulations
This module focuses on the influence of theusing quantum mechanical simulations. The quantum mechanical applications which will be applied in this module are based on density functional theory (DFT). This method allows the investigation of the electronic properties of a system. An understanding of the method, an analysis of the results from the simulations as well as an oral and written presentation is the main goal of this module.
Part 1: Density functional theory and exchange-correlation functionals
This part introduces the students to the density functional theory (DFT) method. A scheme which has revolutionarized the way materials and their properties are studied. The students should focus on this method and understand how it works and which its capabilities are. A specific focus would be the different levels of approximations that can be made in this method. For this, the choice of the exchange-correlation functional mapping the interactions of a system is crucial. To this end, the discussion in this module will be directed. The report should contain an introduction to the exchange-correlation functionals in DFT in the context of the simulations and the analysis of the simulations in Part 2.
- A bird's-eye view of density-functional theory, Klaus Capelle, arXiv:cond-mat/0211443 (2002).
- Self-Consistent Equations Including Exchange and Correlation Effects, W. Kohn and L.J. Sham, , Phys. Rev. (140), A1133 (1965).
- Understanding and Reducing Errors in Density Functional Calculations, Min-Cheol Kim, Eunji Sim, and Kieron Burke, Phys. Rev. Lett. 111, 073003 (2013).
- Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory, J Klimeš, A Michaelides, J. Chem. Phys. 137, 120901 (2012).
- An application of the van der Waals density functional: Hydrogen bonding and stacking interactions between nucleobases, V.R. Cooper, T. Thonhauser, and D.C. Langreth, J. Chem. Phys. 128, 204102 (2008).
- On the accuracy of density-functional theory exchange-correlation functionals for H bonds in small water clusters: Benchmarks approaching the complete basis set limit, B. Santra, A. Michaelides, and M. Scheffler, J. Chem. Phys. 127, 184104 (2007).
- On geometries of stacked and H-bonded nucleic acid base pairs determined at various DFT, MP2, and CCSD(T) levels up to the CCSD(T)/complete basis set limit level, I. Dąbkowska, P. Jurečka, and P. Hobza, J. Chem. Phys. 122, 204322 (2005).
Part 2: Stability and energetics of graphene and H30 radicals
This part is practical and involves the simulation of two different systems: (a) two stacked graphene planes and (b) a H3O radical All simulations will be performed with the software package SIESTA [www.icmab.es/siesta/]. The students should test the use of different exchange-correlation functionals. A thorough analysis of the stability and energetics of the two system is expected.
- From a localized H3O radical to a delocalized H3O+⋯e− solvent-separated pair by sequential hydration, Frank Uhlig, Ondrej Marsalek, and Pavel Jungwirth, Phys. Chem. Chem. Phys., 2011,13, 14003-14009
Please hand in one report per group of 5 to 10 pages containing and discussing your results.
Module 2: Jens Smiatek, Atomistic Simulations of Co-Solutes in Aqueous Solutions
This module focuses on atomistic Molecular Dynamics simulations and the study of biological co-solutes like urea, ectoine or hydroxyectoine and their influence on aqueous solutions. Biological co-solutes, often also called osmolytes are omnipresent in biological cells. A main function of these small-weight organic molecules is given by the protection of protein structures under harsh environmental conditions (protein stabilizers) or the denaturation of proteins (protein denaturants). The underlying mechanism leading to these effects is still unknown. It has been often discussed that osmolytes have a significant impact on the aqueous solution. The module consists of model development, simulation, analysis and oral and written presentation part.
If you have any questions regarding the organization or content of this module please do not hesitate to contact Jens Smiatek.
Part 1: Osmolytes and Kirkwood-Buff Theory
This part introduces the students to the field of osmolyte research. An important theory to study solvation and binding behavior is given by the Kirkwood-Buff theory which can be well applied to computer simulations. The students should study the literature given below and present their findings. The presentation should at a minimum contain an introduction to Kirkwood-Buff theory in the context of the simulations.
- D. R. Canchi and A. E. Garcia, "Co-solvent effects on protein stability", Ann. Rev. Phys. Chem. 64. 273 (2013)
- K. D. Collins, "Ions from the Hofmeister series and osmolytes: effects on proteins in solution and in the crystallization process", Methods 34, 300-311 (2004)
- V. Pierce, M. Kang, M. Aburi, S. Weerasinghe and P. E. Smith, "Recent applications of Kirkwood–Buff theory to biological systems", Cell Biochem. Biophys. 50, 1 (2008)
- J. Smiatek, "Osmolyte effects: Impact on the aqueous solution around charged and neutral spheres", J. Phys. Chem. B 118, 771 (2014)
Part 2: Model Development and Simulations
This part is practical. The simulations will be conducted by the software package . The students will develop Generalized Amber Force Fields (GAFF)  for the osmolytes which will be used for the study of solvent properties like the thermodynamics of hydrogen bonding In comparison to pure water, the students will analyze several water parameters and elucidate the differences in presence of osmolytes and their concentration dependent behavior. The Kirkwood-Buff theory will be used to calculate derivatives of the activity coefficients as well as the osmolyte binding behavior.
- D. van der Spoel, P. J. van Maaren, P. Larsson and N. Timneanu, "Thermodynamics of hydrogen bonding in hydrophilic and hydrophobic media", J. Phys. Chem. B 110, 4393 (2006)
- J. Wang, R. M. Wolf, J. W. Caldwell, P. A. Kollman and D. A. Case, "Development and testing of a general amber force field", J. Comp. Chem. 25, 1157 (2004)
Please hand in one report per group of 5 to 10 pages containing and discussing your results.
Module 3: Christian Holm, Electrostatics and Lattice Boltzmann
This module focuses on charged matter with electrostatic and hydrodynamic interactions. It should be taken in groups of three people. It consists of simulations, theory, a presentation and a short report on the simulation results. You only have to give one common presentation and hand in one report per group. It consists of three parts.
If you have any questions regarding the organisation or content of this module please do not hesitate to contact Christian Holm. For questions regarding the practical part of the module and technical help contact Florian Weik.
Part 1: Electrostatics
This part is about the theory of electrostatic algorithms for molecular dynamics simulations. It is concerned with state of the art algorithms beyond the Ewald sum, especially mesh Ewald methods. To this end the students should read the referenced literature and prepare a 20 minutes presentation. Hold the presentation with Christian Holm and discuss the content and open questions with him. The presentation should contain the students understanding of the P3M method as well as a discussion of its performance compared to other modern electrostatics methods.
Part 2: Slit Pore
This part is practical. It is concerned with the movement of ions in an charged slit pore. It is similar to the systems that are discussed in the Bachelors thesis of Georg Rempfer which is recommended reading. A slit pore consists of two infinite charge walls as shown in the figure to the right. In this exercise you should simulate such a system with ESPResSo. You are supposed to use a Lattice Boltzmann fluid coupled to explicit ions which are represented by charge Week-Chandler-Anderson spheres. In addition to the charge on the walls, the ions are also subject to an external electrical field parallel to the walls. Electrostatics should be handled by the P3M algorithm. A set of realistic parameters and an more in detail description of the system can be found in the thesis. You should measure the flow profile of the fluid and the density and velocity profiles of the ions. The case of the slit pore can be solved analytically either in the case of only counter ions (the so called salt free case) or in the high salt limit (Debye-Hueckel-Limit). Calculate the ion profiles in one or both of these cases and compare the results with the simulation.
Georg Rempfer, "Lattice-Boltzmann Simulations in Complex Geometries" (1.36 MB), 2010, Institute for Computational Physics, Stuttgart
Part 3: Electrophoresis of Polyelectrolytes
In this part you simulate the movement of a charged polymer under the influence of an external electrical field and hydrodynamic interactions. Set up a system consisting of a charge polymer, ions with the opposite charge to make the system neutral and an Lattice Boltzmann fluid coupled the the ions and polymer. Apply an external field and measure the center of mass velocity of the polymer as a function of the length of the polymer for polymers of one to 20 monomers. Make sure the system is in equilibrium before you start the sampling. Compare your result to theory and experimental results (see literature).
Please write together one report of 5 to 10 pages containing and discussing your simulation results from part 2 and 3.