Skip to main content

Physics & Astronomy

Computational Physics at Carthage

Prof. Kevin Crosby

Molecular dynamics (MD) is a computation tool to approximate the interactions between atoms in a variety of materials. These interactions can be quite complex, and the number of atoms in the “computational cell” is typically very large. For these reasons, MD is usually implemented on very powerful computers or on a cluster of linked computers. At Carthage, students have applied MD code to study a variety of problems in material science. We use a cluster of 12 computers shared with the Computer Science Department to run both classical and quantum-ab initio MD code.

Strain Modulation of Band Gaps in Carbon Nanotubes

Carbon nanotube (CNT) structures represent a recently discovered (1991) phase of carbon. The CNT structure is best described as a single graphene sheet rolled into a seamless tube. These single-walled CNTs (SWCNT) can be classified into three categories depending on the geometry of the graphene sheet edge: zig-zag, armchair, and chiral.

The electronic structure of a SWCNT is determined by its geometric properties. Approximately 2/3 of all SWCNTs are semiconducting, while the remainder are insulating. SWCNTs are increasingly studied for their potential uses as ultra-fast transistors and switches in next-generation computing and display technologies. We are studying the modulation of the band gap in SWCNTs with applied tensile strain. The ability to tune the band gap in SWCNT-based devices opens up exciting new possibilities with respect to scale and speed of computing and display technologies.


Ballistic Deposition of Carbon-60 (buckyballs) Molecules 
onto Si-C Substrates

Impact of C-60 molecule on Si substrateImpact of C-60 molecule on Si substrate

The mechanical properties of C-60 molecules make them exciting candidates for a variety of technological applications including drug delivery, high temperature lubricants, wear-protective coatings, opto-electronic devices, and other nanotechnologies. In many of these applications, it is desirable to produce thin films of C-60 molecules adhered to solid substrates. To study the dynamics of C-60 adhesion to a substrate of Si-C, we built and deployed MD code to simulate the ballistic deposition of C-60 molecules on an Si-C substrate over a range of impact parameters. This work resulted in a phase diagram describing the adhesion kinetics as a function of temperature and beam energy.

Structural Phase Transitions in Carbon-60 thin films

C-60 Molecules deposited onto an Si-C substrateC-60 Molecules deposited onto an Si-C substrate

Thin films of C-60 molecules exhibit FCC lattice structures at low temperatures. At higher tempertures, different crystal geometries are produced. In this ongoing project, students explore the nature of the FCC to BCC structural phase transition of C-60 thin films. We are interested in determining the role of lattice defects in this transition.



 Structural Phase Transitions in Carbon-60 thin films

A section of a copper computational cellA section of a copper computational cellA section of a copper computational cell

Thermal self-diffusion in metallic interconnects is a significant technological obstacle to further scale-reduction of integrated circuitry. Diffusion near gain boundaries and other crystal defects is greatly enhanced over bulk diffusion. Using molecular dynamics, we study the processes associated with diffusion near grain boundaries in nano-crystalline copper under tensile stress. A paper describing the essential results of this work isavailable here.

Pictured at left is a section of a copper computational cell showing a coherent twist grain boundary on the central (111) crystallographic plane. The copper crystal is under uniaxial tensile stress applied at the (111) faces.

Molecular Dynamics Studies of Stress Voids in Copper Thin Films

Integrated circuitry relies on the integrity of thin metallic films adhesively bonded to solid substrates. These films, which provide the conducting pathways between transistor elements within the circuit, are increasingly driven to new scales of miniaturization. Typically these films are under very high tensile stress applied by a rigid substrate. These stresses arise from deposition conditions and can be in excess of hundreds of MPa for aluminum and copper films on silicon substrates. High internal stresses are undesirable in most applications and can result in the mechanical failure of the film through the growth of “stress voids” nucleated within the film. Atomic migration is enhanced near such voids leading to open-circuit failure of a current-carrying interconnect. I have a variety of projects related to the investigation of diffusion near such defects under mechanical stress.

  • Quick Facts

    • Carthage is named a Best Midwestern College by The Princeton Review (2021), a designation given to only 25 percent of four-year schools.

    • The Tower, Carthage’s newest residence hall, provides some of the best views on campus — if not in the Midwest! In addition to #carthageviews of the lake from seven stories up, residents enjoy suite-style living and two floors of shared campus spaces for gaming, cooking, group meetings, or quiet studying. Learn more about all housing options.

    • You’re going to need brain fuel. Grab a morning coffee and a snack and Starbucks or Einstein Bros. Bagels. Later, meet friends at “The Caf,” where the specials change daily but the staples are constant, or swing through “The Stu” for wings, a burrito, or a sub. A new option, Carthage Cash, even covers some off-campus meals.

    • More than 90% of Carthage alumni report that they have secured a job or are continuing their studies six months after graduation. Visit The Aspire Center.

    • 91% of employers say critical thinking, communication, and problem-solving skills matter more than your major when it comes to career success. Learn more about how the liberal arts prepare you for a successful career.

    • Lots of schools wear the four-year label. Carthage stands behind it. More than 90% of Carthage graduates earn their degrees in four years. Learn more

    • Computer science students watch Prof. Mark Mahoney’s recorded lecturers in their free time, so he can nearby “when they do their real learning,” he says. He has company: Physics professor Brant Carlson’s quantum mechanics video playlist has been viewed more than 170,000 times. 

    • Oscars. Emmys. Tonys. Golden Globes. The playwrights we’ve brought in have them. Each year, the Carthage Theatre Department commissions an original script by a renowned playwright for its New Play Initiative. Carthage students then work with the writer to stage it. 

    • Carthage has ranked as a top Fulbright producer for four of the past five years. Read about Carthage Fulbright winners.

    • Things look new at Carthage because they are. Our science center, student union, athletic and recreation center, and numerous residence halls have all been constructed or newly renovated in the last 15 years.

    • Carthage offers majors, minors, and concentrations in more than 50 areas of study, from marketing to neuroscience, nursing to music theatre.

    • Our Summer Undergraduate Research Experience offers select students a research budget, one-on-one mentoring with a professor, and 10 weeks of analyzing, deciphering — and getting paid.

    • So the lake is kind of a focal point, but there’s a lot more to love about our campus — like the fact that our more than 80-acre campus is also an arboretum and wildlife sanctuary. Focused on keeping campus lush forever, we plant between 50 and 75 new trees every year from a variety of species.

    • Carthage was founded in 1847. That’s more than 170 years of leaders, makers, and go-getters going out and going forth. Read more about Carthage’s rich history.

    • More than 90 percent of students receive financial aid. Carthage awards more than $20 million in scholarship and grant assistance. That includes $5.5 million in competitive scholarships in business, mathematics, science, languages, the fine arts, leadership, and overall academic strength. Learn what’s available.

    • Abraham Lincoln was an early Trustee of the College, and U.S. Secretary of State John Hay was a Carthage alum. The two still have a proud place on our campus. Spend some time with them in our Sesquicentennial Plaza. On warm days you’ll find professors leading their classes here.

    • Come to Carthage; hear yourself think — think … think …
      Legend has it that Sesquicentennial Plaza holds a perfect echo. Just stand with both your feet on the “1847,” face Straz, and start talking. “You’re the only one who can hear you, but you’ll be crystal clear,” promises English and theatre alumna Mikaley Osley.

    • Our Great Lake provides Carthage students with some amazing views. Think classes on the beach, lake views from the lab, and sunrises from your dorm room. “I love waking up in the morning with the sun shining off the lake. Nothing compares to the view in the morning,” recalls biology and neuroscience major Ann O’Leary.

    • Carthage awards up to 35 Presidential Scholarships each year, which range from $25,000 up to full tuition. Learn more.

    • For a full decade, NASA has selected Carthage students to conduct research aboard its zero-gravity aircraft. Lately, the stakes have risen. A team of underclassmen is grinding to prepare a tiny but powerful Earth-imaging satellite for launch to the International Space Station. Learn more about the space sciences at Carthage

    • Carthage is the only college or university in the Midwest where every freshman takes a full-year sequence of foundational texts of the Western intellectual tradition. Learn about Intellectual Foundations.

    • With a student-faculty ratio of 13:1, your professors will know who you are. They will also know who you want to be — and how to get you there. Meet our faculty.

    • There are more than 130 student organizations on campus, from Amnesty International to Fencing to Frisbee, Chem Club to Stand Up Comedy. See how easy it is to get involved.

    • True story: There are more than 27 art galleries, a dozen museums, and nine theatres within 25 miles of Carthage. Some highlights: The nationally recognized Racine Art Museum, the world-renowned Art Institute of Chicago, and the Milwaukee Art Museum. Learn more about our location.

    • What’s better than one professor? Two professors. What’s better than two professors? Two professors from totally different fields teaching a single class. There’s debate. Discussion. Differing perspectives. This is where the magic happens. That’s why every student takes a Carthage Symposium.

    • You can’t hide here — not with only 17 other students in the classroom with you. That’s going to be rough some mornings. But later, when you’re able to argue your point of view thoughtfully, express your opinions succinctly, and meet challenges head-on, without fear … Yep, you’ll thank us.

    • Carthage is ranked in the Top 5 in the country for student participation in short-term study abroad. Every J-Term, hundreds of students travel all over the world on faculty-led study tours. Imagine a month in Sweden, Rome, Cuba, Senegal, India, Japan …