1. Design of metal nanoclusters as catalyst for Fischer-Tropsch Reaction
Sumegha Godara
Dr. Daniela Mainardi
Louisiana Tech University
June, 2017 3

2. Introduction: Metal nanocluster Models
Black box
of Catalysts
Long-chained hydrocarbons
CO + H2
nCO + (2n+1)H2  CnH2n+2 + nH2O
55 atom nanoclusters (D ~ 1 nm):
With DFT implemented in VASP Ru Pt Pd Co Ni Fe
Carbon monoxide adsorption energies were calculated for adsorption on all possible catalytic sites, and the most preferred CO adsorption sites were found in each case.

3. Increased cluster model size
Selection Process of Catalyst Model
Energy Barrier
CO dissociation
CO adsorption
D ~ 0.5 nm
(13 atoms)
D ~ 1.5 nm
(55 atoms)
D ~ 0.9 nm
(38 atoms)
D ~ 2.0 nm
(309 atoms)
Increased cluster model size
Our Approach is to study the CO adsorption and dissociation on bigger metal cluster to have more realistic results as we only have studied this on the smallest stable cluster of 13 atoms. And also apply that % difference on bimetallic clusters to see how they behave.
Best metallic catalyst ??
Can this be used to predict binary systems’ behavior?

4. Scaling of # of cores in VASP
On QueenBee2 LONI : 1 node:20 cores
Not all elements are good for everything, there are metals that produce hydrocarbons, others produce oxygenate species, and Rh produces ethanol
As I mentioned before the metals that exhibit FT catalytic activity are placed in order here, but for practical purposes, iron and cobalt are the best.
If you take a look at their cost, you will see…
An idea to reduce cost is to use core-shell nanocatalysts
That is possible if the elements segregate
In any other case, it will be a mixture/ alloy

5. Future work (Parallelization with MPI)
Initial (random) configuration
Final (most probable) configuration found
Molecular Dynamics simulation
NVE ensemble
(to relax the structure)
A Python code was written
Random atomic initial configuration
A Monte Carlo allows to find the most probable arrangement of atoms
A system thermalization (heat treatment) is performed via Molecular Dynamics.
Kinetic energy is given to the system according to a Maxwell-Boltzmann distribution at T0 and the system evolves to a relaxed structure.
We optimized the 55 atom clusters and the CO adsorption and diss studies are in process. A python code was written to see the thermal stability of the clusters in which a random ….

6. Acknowledgements The Mainardi Research Group at
Louisiana Tech University
Financial/Computational Support provided by
US National Science Foundation,
NSF-CREST, Grant HRD
NSF LA-SiGMA, EPS
NSF CAREER, Grant CTS
NSF IMR, Grant DMR
Louisiana Board of Regents, Contract LEQSF( )-ENH-TR-46
The Louisiana Optical Network Initiative (LONI)
PhD Students
Suraj Gyawali
Shawn Cole
Sumegha Godara
Dr. Purnima Kharidehal
Dr. Fernando Soto
MS Students
Sajin Killa
King-Ki Fung, MS
Visiting Researchers
Alaina Fox – REU Summer’15
Mary Beth McCoy– RET Summer 2015 – Sterlington Middle and Ouachita Junior High School, LA

7. Questions?