School of Physics and Astronomy

Dr Alston Misquitta, PhD, Delaware (2004) MA, Cambridge (2011)

Alston

Lecturer in Condensed Matter and Materials Physics

Email: a.j.misquitta@qmul.ac.uk
Telephone: 020 7882 3427
Room Number: G.O. Jones Building, Room 216
Website: https://app.ph.qmul.ac.uk/wiki/ajm:camcasp:start
Office Hours: These change from semester to semester but will usually be: Mondays: 1pm to 2pm Wednesdays: 1pm to 2pm

Profile

My primary expertise is in the field of intermolecular interactions. Here I have made major advances in the fundamental electronic structure methods that are used. One of these is the symmetry-adapted perturbation theory based on density-functional theory, or SAPT(DFT). I have also developed advanced methods for computing molecular properties in distributed form: these include the ISA-DMA multipole moments, ISA-Pol frequency-dependent polarizabilities and dispersion models, andWSM polarizabiliity and dispersion models. All of these methods, as well as key methods to combine them to generate intermolecular force-fields, are implemented in the CamCASP program which has been written by me and my long-term collaborator, Prof. Anthony Stone (Cambridge). 

Websites:

 Some of the recent developments I have played a major role in includes:

  1. Development of the MASTIFF and SlaterFF models in collaboration with Prof JR Schmidt (Madison)
  2. ISA-Pol algorithm for distributed frequency-dependent polarizabilities.
  3. ISA-DMA multipoles that are proving to be some of the most accurate available. 
  4. Many-body interaction models in CamCASP, with applications to the pyridine crystal. We found a third form of the pyridine crystal using the model derived from CamCASP.
  5. Anomalous dispersion models in trimers of 1D wires. This is a follow-on from a previous ground-breaking work on dispersion interactions in pairs of 1D wires
  6. Following on from earlier work on soot formation in combustion engines, we have begun exploring new and novel mechanisms to try to explain how PAHs aggregate to form black carbon. This is collaboration with Prof Markus Kraft and his group in Cambridge. For an overview of the issues see this paper on soot formation. 

Collaborators & Friends

  1. Prof Anthony J. Stone (Cambridge)
  2. Prof Sally L. Price (UCL)
  3. Prof Markus Kraft (Cambridge)
  4. Prof Jean-Philip Piquemal (Sorbonne)
  5. Dr Rachel Crespo-Otero (SBCS, QMUL)
  6. Prof Piotr Zuchowski (Torun, Poland)
  7. Dr John Dennis (SPA, QMUL)
  8. Prof Martin Dove (SPA, QMUL)

Teaching

Current teaching:

Previous Teaching:

  • Scientific Laboratory (SPA4018)
  • Synoptic Physics
  • Computational Condensed Matter Physics

 

Research

Research Interests:

A. Research Summary

The main focus of my research is the field of intermolecular interactions.  I work on both the theoretical and computational aspects of this subject, and have made significant contributions to this field through the development of SAPT(DFT) (a symmetry-adapted perturbation theory based on density functional theory) and the Misquitta-Williams-Stone (WSM) method for molecular properties.

These methods---now in use by a number of research groups worldwide---have been made available to the community through the SAPT and CamCASP programs, the latter of which I am the lead author.

In brief, SAPT(DFT) (also known as DFT-SAPT) is an electronic structure method for calculation of intermolecular interaction energies that has a computational cost similar to MP2 but an accuracy close to CCSD(T) (one of the most advanced and accurate electronic structure methods that can be applied to moderately sized problems). 

Additionally, the interaction energy from SAPT(DFT) is naturally split into physical components, such as the electrostatic, exchange, polarization and dispersion energies. This, combined with accurate distributed molecular properties from the WSM method, allow the construction of analytic potentials and provide a deep insight into the physical processes of molecular aggregation.

I work on the development and application of these methods. Currently my projects include:

  • Potentials: Using SAPT(DFT) and the WSM methods to calculate very detailed intermolecular potentials. These include the effects of atomic anisotropy and polarizability.
  • Organic Crystals: These potentials can then be used to predict the most stable structures of small ro meduim-sized organic molecules. Together with the group of Prof. Sally Price (UCL) and Prof Anthony Stone (Cambridge), I have been able to predict the crystal structure of C6Br2ClFH2 in the 2007 Blind Test of Crystal Structure Prediction organised by the CCDC. This was quite an achievement - the first for a completely ab initio method.
  • Small-gap, extended systems: The interactions between extended (1 or 2-dimensional) systems with small HOMO-LUMO (band) gaps is qualitatively different from that between insulators. This was a significant result of some very recent work I have done with Ali Alavi, James Spencer and Anthony Stone. This has opened up a lot of possibilities as small-gap systems like carbon nanotubes and organic molecular wires are the basic components of a lot of work on nano-fabrication and nano-devices.
  • Dispersion-corrected DFT: I am also currently working on very accurate dispersion corrections for DFT methods specifically applicable to water ice. My goal here is to achieve far higher accuracies than has been possible so far. The SAPT(DFT) and WSM methods are crucial here as I derive all parameters based on theory alone. This work, which is in it's final stages, can be readily extended to other systems.
  • Soot: Soot particles are aggregates of polyaromatic
    hydrocarbons (planar molecules of carbon and hydrogen atoms). Even at 2000K, the temperature in a petrol engine, the attractions between
    such molecules can be strong enough to cause them to aggregate, forming elementary soot particles. In collaboration with  Tim Totton, Markus Kraft (both in Chemical Engineering) and Dwaipayan Chakrabarti (Chemistry), I am trying to provide a detailed description of the structure and dynamics of these particles, and thence to understand the behaviour of reactant gases within them. This information, which cannot be obtained experimentally, is crucial for engine modelling, and could result in engines that produce little or no soot. There are important reasons why we need this: one is that smoke inhalation is the cause of many deaths (around 400,000 in India alone), and another is that soot is now thought to be second only to carbon dioxide in its effect on global warming, through its ability to absorb radiation in the upper atmosphere (Myhre, Science,2009).
    Because soot has a lifetime of just a few days, improvements to combustion engines will have an almost immediate impact on global climate.

B. Click here for Full Publication List (ResearchID) or my publications on Google Scholar

The Google Scholar page is usually more up-to-date and does not need a login to see the contents. I an active on Research Gate where you can find my papers as well as other information. 

C. Selected Articles

A. J. Misquitta and A. J. Stone, ISA-Pol: distributed polarizabilities and dispersion models from a basis-space implementation of the iterated stockholder atoms procedure, Theoretical Chemistry Accounts 137 (11), 153. (This paper is in a special collection dedicated to the memory of a a friend and colleague: Dr Janos Angyan)

A. A. Aina, A. J. Misquitta, S. L. Price, From dimers to the solid-state: distributed intermolecular force-fields for pyridine, The Journal of chemical physics 147 (16), 161722

A. J. Misquitta and A. J. Stone, Ab initio atom-atom potentials using CamCASP:  Theory and application to many-body models for the pyridine dimer',  J. Chem. Theor. Comput., 12,  4184--4208 (2016).

A. J. Misquitta, J. Spencer, A. J. Stone and A. Alavi. Dispersion interactions between semi-conducting wires, Phys. Rev. B, 82, 075312-7 (2010).

A. J. Misquitta, G. W. A. Welch, A. J. Stone and S. L. Price. A first principles prediction of the crystal structure of C6Br2ClFH2, Chem. Phys. Lett. 456, 105(2008).

A. J. Stone and A. J. Misquitta. Atom-atom potentials from ab initio calculations, Int. Rev. Phys. Chem. 26, 193(2007).

A. J. Misquitta, B. Jeziorski, and K. Szalewicz. Dispersion energy from density-functional theory description of monomers, Phys. Rev. Lett. 91, 033201(2003).

A. J. Misquitta and K. Szalewicz. Intermolecular forces from asymptotically corrected density functional description of monomers, Chem. Phys. Lett. 357, 301(2002).

D. Software

CamCASP is a collection of scripts and programs for the calculation ab initio of distributed multipoles, polarizabilities, dispersion coefficients and repulsion parameters for individual molecules, and interaction energies between pairs of molecules using SAPT(DFT). Authors: A. J. Misquitta and A. J. Stone. Web site: http://www-stone.ch.cam.ac.uk/  For the CamCASP wiki see this link.

SAPT2008: An Ab Initio Program for Many-Body Symmetry-Adapted Perturbation Theory Calculations of Intermolecular Interaction Energies. Web site: http://www.physics.udel.edu/ szalewic/SAPT.

Funding

Recent funding:

My interaction on both these projects is focused on bringing first-rinciples force-fields and the very latest developments in Intermolecular Interactions into the models used in simulations with the Tinker and Tinker-HP codes. My collaborators here are Prof Jean-Philip Piquemal (UPMC, Sorbonne) and Dr Louis Lagardere (CNRS). 

Publications

PhD Supervision

Research Group

  1. Lei Tan (PhD candidate) : Lei is working on methods for exloring the structure-space of functionalised quantum nanodots. She uses a variety of methods to find candidate structures of CdSe and CdS dots, and is active in developing new and novel techniques to map out the energy landscape of these technologically important materials.
  2. Alex Aina (PhD candidate) (AWE funded through UCL) : Alex is working on using ab initio models derived using CamCASP to explore the crystal energy landscape of energetic materials. He is interested in the issues of molecular conformation flexibility on the models, and seeks to find robust methods to make the development of polarizable models easy. Alex has found a third form of pyridine during the course of one of his studies. 
  3. Tong Liu (PhD candidate) : Tond is working on functionalised fullerenes and is interested in their use as efficient photo-voltaic devices. She has used TDDFT to study the conformer-excitation energy relation and has developed a scheme for tuning the range-separation parameter for these materials.
  4. Harry Campion (Master's project student) : Harry has worked on the linear-response kernel used in SAPT(DFT). He is currently working on an alternative for the problematic delta-HF term in SAPT and SAPT(DFT). He is also interested in charge-transfer and is making a systematic study of the charge movement in strongly bound complexes. 
  5. Gianluca Cientanni (Master's project student) : Gianluca is working on a Python project to better handle the large amounts of data we produce in our calculations. He has written a set of functions around a JSON database with which data collection, querying and visualisation will be made easy. The goal here is to facilitate research by making data-handling quick and easy.
  6. Soumik Ghosh (EuroMasters) : Soumik is working on aspects of the van der Waals models for low-dimensional systems. He seeks to understand how these models behave as the HOMO-LUMO gap closes, and is using the ISA-Pol model to develop and analyse the dispersion models.
  7. Frasier Ng Zu Quan (Master's project student) : Frasier is delving into a recent controversary in the field. It has been shown that in confinement the van der Waals energy can be repulsive. This is a surprise as it has been so far thought to be always attractive at the two-body level. Frasier is hoping to shed some light on the problem by replicating and cross-checking the derivation. 

Research Projects on offer

For my primary research interests see my Research Pages. You will get a good idea of the kinds of research projects at hand from there. Here are some example projects (that are usually out of date!) I would be happy to discuss other project possibilities.

Project TitleDescription 
A new generation of interaction models This is a constant topic of research. We are always seeking to improve our interaction models and make them every more accurate and predictive. This kind of research is often done in collaboration with some of my colleagues (in the UK, France, or elsewhere) who apply these models to complex and challenging systems.  
Ab initio methods for electronic charge-transfer Charge-transfer (CT is one of the more controversial ideas in the field of intermolecular interactions. A lot of research groups try to define it and while they sometimes agree, more often they do not. But the CT energy  is very important in strongly polarizable systems such as water, or any system with strong hydrogen bonding, and perhaps even more generally when weak covalent bonds start to form. We need a good physical model to account for this energy and we need to be able to compute it accurately (what ever this means). The CT energy forms the basis of the polarization models I develop. In this project we will explore many ideas for calculating the CT energy and the charge transfered, and hopefully use this knowledge in better and more accurate many-body models.

Interaction energy models based on the denstiy

We undertsand how to create detailed and accurate many-body interaction models based on SAPT(DFT) and very accurate distributed molecular properties (multipoles, polarizabilities) all computed from first-principles. But though we have made strides in making this much easier than it once way, it is still tedious. Here we will attempt to make many of these steps easier by using information theory and machine learning.

Intermolecular interactions in a excited state

Here we will develop new methods/codes for evaluating the interaction energy in systems where one or more molecule is in an excited state. This is a project in collaboration with Dr Rachel Crespo-Otero (SBCS, QMUL), and Prof Piotr Zuchowski (Torun, Poland). Here we will combine perturbative and non-perturbative methods to develop a new method that will allow us to explore interactions in systems that are photo-excited. This is a new and very exciting field of research. 

 

Performance

Selected Invited Talks

  1. 2019: Institute for Chemisty at the University of Graz (Boese group)
  2. 2019: Invited talk in Molecular Properties at ISTCP 2019, the 10th Triennial Congress of the International Society for Theoretical Chemical Physics to be held in Tromsø. 
  3. 2019: Invited talk at the Tinker-CHARMM meeting in Paris.
  4. 2018: Invited talk at Nicholas Copernicus University in Torun. In the group of Prof Piotr Zuchowski.
  5. 2017: Invited talk at the TSRC workshop on Intermolecular Interactions held in Arenas de Cabrales, Spain. 
  6. 2017: Invited talk at the CESTC meeting in Wisła, Poland.

Apart from these, I am a regular speaker at CECAM and TSRC workshops and have given numerous talks around the UK and in the US and other EU contries (Germany, France, Poland).

Conferences Organised

  1. 2016: CECAM workshop on Density- and Response-density -based models for Intermolecular Interactions in Molecular assemblies and solids. Organised in Nancy together with Janos Angyan, Dario Rocca and Andreas Hesselmann. 

Visiting positions

  1. 2017: Visiting professorship at UPMC, Sorbonne, in the group of Prof. Jean-Philip Piquemal.
  2. 2014: Visiting professorship at Université de Nancy, in the group of Dr Janos Angyan.