** Reference to paper:

J. Chem. Phys. 149, 094701 (2018)

** DOI:

10.1063/1.5046065

** Title:

Methane on a stepped surface: Dynamical insights on the dissociation of CHD3 on Pt(111) and Pt(211)

** Authors:

Davide Migliorini, Helen Chadwick, and Geert-Jan Kroes

** Contact e-mail:

d.migliorini@lic.leidenuniv.nl

** Abstract:

The simulation of the dissociation of molecules on metal surfaces is a cornerstone for the 
understanding of heterogeneously catalyzed processes. However, due to high computational demand, 
the accurate dynamical simulation of the dissociative chemisorption of polyatomic molecules has 
been limited mostly to flat low-index metal surfaces. The study of surfaces that feature “defected”
sites, such as steps, is crucial to improve the understanding of the overall catalytic process due 
to the high reactivity of under-coordinated sites for this kind of reaction. In this work, we have 
extensively analyzed more than 10 000 ab initio molecular dynamics trajectories where a CHD3 
molecule is impinging either on the flat Pt(111) surface or on the stepped Pt(211) surface for 
different initial rovibrational states and collision energies. The results have been compared in 
order to get insight into the effect of the step in the dissociation of methane. We have found that, 
despite a large difference in the activation barrier and consequently in reactivity, the geometry 
of the lowest transition states is very similar on the two surfaces and this results in a similar 
dissociation dynamics. Furthermore, the trapping observed on the Pt(211) surface can be explained 
with energy transfer to parallel translational motion induced by the geometry of the slab and by a 
larger energy transfer to phonons for the stepped Pt(211) surface.

** Description per file:

- 	JCP_Main_Paper.pdf is the paper in pdf (preprint format).

- 	SupplementaryMaterial.pdf is the published suppoting information.

- 	The material is divided in directories corresponding to the various 
	tables/figures in the paper. 

-	The programs and scripts used to set up AIMD calculations have been reported 
	previously and they can be found in ../2017-JPCL-8-4177/AIMD

-	the files called RESULTSXXX.dat, where XXX is the fcc surface (111 or 211, respectively)
	contain a database of most of the observables reported in the paper. If not stated differently
	these files contains the quanties plotted and reported in the tables of the paper.
	The database contains, for each trajectory:

	FUNC		Functional used (SRP stands for SRP32-vdW)
	STATE		if the molecule comes from a laser-off (LO) of v1=1 set of trajs 
	Ei		average beam collision energy of the set
	N		trajectory number
	OUTCOME		the outcome
	BOND		the bond broken
	BOUNCES		number of bounces
	STEERING	dCOM as defined in the paper (lateral displacement on the way to the surface)
	XYdist		distance travelled in the XY plane
	Xdist		distance travelled in the X direction
	Ydist		distance travelled in the Y direction
	DISP		total lateral displacement
	DIST2Pt_I(F)	distance in xy from the closest 1st layer atom t the initial (I) and at the final (F) step
	THETA_I(F)	theta at the initial (I) and at the final (F) step, as defined in the paper 
	BETA_I(F)	beta at the initial (I) and at the final (F) step
	GAMMA_I(F)	gamma at initial (I) and at the final (F) step
	COM_I(F)x	center of mass X coordinate the at initial (I) and at the final (F) step
	COM_I(F)y	center of mass Y coordinate the at initial (I) and at the final (F) step
	Site_I(F)	surface site above which the COM sits at the at initial (I) and at the final (F) step
	FACET_I(F)	surface facet above which the COM sits at the at initial (I) and at the final (F) step
	<Vxy>		average velocity in the xy plane (as defined in the paper)
	<Vx>		avreage velocity in the x direction (as defined in the paper)
	Kxy		final kineitic energy (as defined in the paper)
	ALPHA_I(F)	alpha at initial (I) and at the final (F) step

	**** the database contains 'None' if an observable has not been computed for a particular trajectory.

N.B.    all the calculations using a functional of the vdW-DF family need to be performed with an additional
        input file called vdw-kernel.bindat. If the file is missing VASP will compute it before starting the 
        actual calculation but this can take a lot of time (even days)