Download Midterm 6/24/15 Research Presentation

LAMMPS
Simulation of
Tungsten
Trioxide
By: Sarah Bartley
Research Mentor: Dr. P. Misra
REU Team members: Dr. D.
Casmir, R. Garcia-Sanchez, and
C. Craig
REU 2015
Howard University 2400 Sixth St
NW, Washington, DC 20059
Outline
 Background
Gas Sensors
o Raman Spectroscopy
o Molecular Dynamics
 Methodology
 Goals for the next 5 weeks
o
What are gas sensors?
 It
measures the concentration of gases.
Each gas causes a particular voltage
change that enables the substrate to
become electrically conductive.
 Example: Alcohol breath tests
Qualities of Gas Sensors
 High
Sensitivity
o Surface-to-volume ratio
 High Selectivity
 Stability
o Mechanical and chemical
 Low cost to manufacture
Tungsten Trioxide Gas Sensor
 Able
to detect nitric oxide and nitrogen
dioxide in temperatures of 200 ˚C – 300 ˚C.
 Nitrogen Dioxide is a toxic gas is fatal due
to inhaling. It is typically associated with
respiratory problems.
Raman Spectroscopy with Gas
Sensors
 Explore
the sensitivity of gas sensors.
 Temperature’s impact on the Raman
spectra.
 Gas sensors have a optimal operating
temp.
 Increase in temperature decreases
Raman intensity.
Why Model Raman Spectra?
 Currently
we are observing temperature's
impact on tungsten trioxide.
 You can analyze the stretching and
bending of the molecule with the Raman
spectra.
 Models in LAMMPS makes this process
easier to observe.
What is LAMMPS?
 LAMMPS
is a computer program that
models the physical interaction between
atoms and/or molecules. LAMMPS can be
used to simulate experiments between
atoms and molecules. Its output data can
be used to compare to the experimental
data.
LAMMPS Models
LAMMPS NVE Simulation
Using LAMMPS to make WO3
Running
file
Number of
atoms and
bonds
Issues with Tungsten Trioxide
 In
the input data file, all the atoms are not
connected properly.
 VMD makes crude approximations about
the bonds.
NVE Simulation
Overview of NVE Sim.
NVE Simulation
Goals
 With
the use of fix commands, I can
regulate the temperature.
 Temperature experiments displays the
molecule vibrating at different
temperature.
 It gives a closer look into the stability of
the molecule.
Acknowledgment
 NSF
for funding
 Dr. D. Casmir for assistance with LAMMPS
 Research Mentor: P. Misra
 REU Teammates: Dr. D. Casmir, R. GarciaSanchez, C. Craig
References




Garcia-Sanchez, R., Ahmido,T., Casimir, D., Baliga, S., & Misra,P. (2013).
Thermal Effect Associated with the Raman Spectroscopy of WO3 Gas
Sensor Materials. The Journal of Physical Chemistry, 117 (1),13825-13831.
Retrieved from http://pubs.acs.org/doi/ipdf/10.1021/jp408303p
Ponzoni,A.,Comini,E.,Sberveglieri,G.,Zhou,J.,Deng,S.,Xu,N.,Ding,Y., &
Wang,L.(2006). Ultrasensitive and highly selective gas sensors using threedimensional tungsten oxide nanowire networks. AIP Scitation. Advance
online publication. Doi : 10.1063/1.2203932
Barsan, N., Koziej, D.,& Weimar,U.(2006). Metal oxide-based gas sensor
research: How to?. Science Direct, 121(1), 18-35. Retrieved from
http://www.sciencedirect.com/science/article/pii/S0925400506006204
Xie,S.,Iglesia,E.,& Bell,A. (2001). Effects of Temperature on the Raman
Spectra and Dispersed Oxides. ACS Publication, 105(22),5144-5152.
Retrieved from http://pubs.acs.org/doi/pdf/10.1021/jp004434s