POSTDOCTORAL POSITIONS AVAILABLE

I am looking for TWO postdoctoral research associates interested and qualified to work in the areas described below.  The positions are available immediately.  The term is one year with additional years possible subject to mutual consent. A description of my research interests is attached.

Potential candidates should provide a statement of qualifications, period of availability and arrange for three letters of recommendation.  While expertise in nuclear dynamics is desirable, expertise in modern electronic structure theory is a must.   My e-mail address is given below.

David R. Yarkony
Chair & D. Mead Johnson Professor of Chemistry
Department of Chemistry
Johns Hopkins University
Baltimore, MD 21218
Email:	[log in to unmask]

NONADIABATIC ELECTRONIC STRUCTURE AND NUCLEAR DYNAMICS

My research deals with electronic structure and dynamics aspects of nonadiabatic processes.  In the electronic structure arena my work deals with both fundamental issues and practical concerns including  
(i) construction of full dimensional diabatic representations fit to ab initio electronic structure data, energies, energy gradients and derivative couplings which include dynamical correlation often  lacking in nonadiabatic dynamics; 
(ii) diabolical singularities, singularities in the adiabatic to diabatic states transformation owing to spurious singularities in molecular properties based defining equations,
(iii) what I believe will turn out to be most impactful, the Geometric Phase(GP)/Molecular Aharanov Bohm (MAB) effect in nonadiabatic tunneling.  In this case, despite the fact that single adiabatic surface dynamics is expected to be valid the existence of a GP effect due  to energetically inaccessible conical intersections destroys the relation between barrier heights and tunneling rates!   To address this fundamental issue we will develop, with Hua Guo of the University of New Mexico, one and two state nuclear dynamics algorithms which include the vector coupling terms, obtained from 2 state diabatic representations (see (i)), needed to take proper account of the GP effect. 
(iv) Further our fit coupled diabatic representations (see (i) ) will be combined with exact reduced dimensionality nonadiabatic quantum dynamics carried out in collaboration with Hua Guo of the University of New Mexico, to produce nonadiabatic dynamics with unprecedented accuracy.

A key aspect of our approach to accurate nonadiabatic dynamics and proper inclusion of the vector potential, in adiabatic states dynamics, is the method we have developed for determining quasi-diabatic coupled electronic state Hamiltonians Hd to treat multichannel dissociative systems.  This methodology determines a full dimensional diabatic representation, Hd that provides a least squares fit to the ab initio adiabatic state data energies, energy gradients and derivative couplings, based exclusively on multireference single and double configuration interaction (MRCISD) wave functions.  See

On the Elimination of the Electronic Structure Bottleneck in On the Fly Nonadiabatic Dynamics for Small to Moderate Sized (10-15 atom) Molecules Using Fit Diabatic Representations Based Solely on ab initio Electronic Structure Data:  The Photodissociation of Phenol
	Zhu, X.; Yarkony, D. R. J. Chem. Phys 144, 024105 (2016)

In addition to providing accurate representations of ab initio electronic structure data obtained exclusively at the MRCISD level, for use in multistate nonadiabatic dynamics, when only two electronic states are considered the resulting Hd enables treatment of single adiabatic state tunneling impacted by the GP effect attributable to energetically inaccessible conical intersections. Such tunneling is normally, but possibly incorrectly, treated using the standard Born-Oppenheimer approximation.   For electronic structure aspects, see

On the Incorporation of the Geometric Phase in General Single Potential Energy Surface Dynamics: A Removable Approximation to Ab Initio Data
Christopher L. Malbon, Xiaolei Zhu, Hua Guo and David R. Yarkony, J. Chem. Phys. 145, 234111 (2016)

and for dynamics aspects, see:
Constructive and Destructive Interferences in Nonadiabatic Tunneling via Conical Intersctions
Changjian Xie, Brian K. Kendrick, David R. Yarkony and Hua Guo J. Chem. Theo. Comput. 13, 1902-1910 (2017)

One of the major goals of our research is to determine  the prevalence of the inadequacy  of the single state Born-Oppenheimer approximation in dissociative systems  owing to energetically inaccessible  conical intersections

Photoelectron Spectrosscopy
The final area to be treated is the photoelectron spectrum arising from electron detachment from anions.  In two papers with Michael Schuurman, we significantly extended the range of systems, which could be treated by introducing fine-grained parallelism, and a more general expansion approach for the residual state based on generating functions.
  			
A method to reduce the size of the vibronic basis employed in the simulation of spectra using the multimode vibronic coupling approximation
	 Michael S. Schuurman and David R. Yarkony, J. Chem. Phys. 128 044119 (2008)
  			
On the Multimode Quadratic Vibronic Coupling Model.  An Open-ended Solution to the Secular Problem Using a Parallel Lanczos Algorithm 
	Michael S. Schuurman, Richard A. Young  and David R. Yarkony,  Chem. Phys. 347, 57-64 (2008)
  			
Using these tools we soon produced the nonadiabatic photoelectron spectrum of  pyrazolide a system that had been declared intractable using the then state of the art techniques
  			
	A simulation of the photoelectron spectrum of pyrazolide,
	Michael S. Schuurman and David R. Yarkony, J. Chem. Phys, 129 064304  (2008).


We will now extend the capabilities of the algorithm to include angular distributions of the ejected electron, a generalization of the adiabatic state Dyson orbital approach of Krylov to nonadiabatic systems.  To accomplish this one needs to compute the scattering orbital of the residual molecule with outgoing wave boundary condiions.  The lowest order approximation to this orbital is the plane wave  .  A more  complete discussion is found in a series of papers culminating in:

	A Lippmann – Schwinger Approach for the Determination of Photoionization and Photodetachment Cross Sections Based on a Partial Wave Green’s Function Expansion and Configuration Interaction Wave Functions.
	Seungsuk Han and David R. Yarkony, Mol. Phys.  110, 845-859 (2012).

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