Category: blog

May 29 2016

One more digit of importance

Over the past few weeks I have bumped into several issues each tracing back to numerical accuracy. Although I have been  programming for almost two decades I never had to worry much about this, making these events seem as-if the universe is trying to tell me something.

Now, let me try to give a proper start to this story; Computational (materials) research is generally perceived as a subset of theoretical (materials) research, and it is true that such a case can be made. It is, however, also true that such thinking can trap us (i.e. the average computational physicist/chemist/mathematician/… programming his/her own code) with numerical accuracy problems. While theoretical equations use exact values for numbers, a computer program is limited by the numerical precision of the variables (e.g. single, double or quadruple precision for real numbers) used in the program. This means that actual numbers with a larger precision are truncated or rounded to the precision of the variable (e.g. 1/3 becomes 0.3333333 instead of 0.333… with an infinite series of 3’s). Most of the time, this is sufficient, and nothing strange will happen. Even more, most of the time, the additional digits would only increase the computational cost while not improving the results in a significant fashion.

Interstellar disc

To understand the importance, or the lack thereof, of additional significant digits, let us first have a look at the precision of \pi and the circumference and surface area of a disc. We will be looking at a rather large disc, one with a radius equal to the distance between the sun, and the nearest star, Alpha Centauri, which is 39 900 000 000 000 km away. The circumference of this disc is given by 2r\pi (or 2.5 \times 10^{14} km ). As a single precision variable \pi will have about 7-8 significant digits. This means the calculated circumference will have an accuracy of about 1 000 000 km (or a few times the distance between the earth and the moon). Using a double precision \pi variable, which has a precision of 16 decimal digits, the circumference will be accurately calculated to within a few meters. At quadrupal precision, the \pi variable would have 34 significant decimal digits, and we would even be able to calculate the surface of the disc ( r^2\pi or 5.0 \times 10^{33} m² ) to within 1 m². Even the surface of a disc the size of our milky way could be calculated with an accuracy of a few hundred square km (or ± the size of Belgium ).

Knowing this, our mind is quickly put at easy regarding possible issues regarding numerical accuracy. However, once in a while we run into one exceptional case (or three, in my case).

1. Infinitesimal finite elements

Temperature profile in the insulating layer of a cylindrical wire.

Temperature profile in the insulating layer of a cylindrical wire.

While looking into the theory behind finite elements, I had some fun implementing a simple program which calculated the temperature distribution due to heat transport in an insulating layer. The finite element approach performed rather nicely, leading to good approximate results, already for a few dozen elements. However, I wanted to push the implementation a bit (the limit of infinite elements should give the exact solution). Since the set of equations was solved by a LAPACK subroutine, using 10 000 elements instead of 10 barely impacted the required time (writing the results took most of 2-3 seconds anyway). The results on the other hand were quite funny as you can see in the picture. The initial implementation, with single precision variables, breaks down even worse already at 1000 elements. Apparently the elements had become too small leading to too small variations of the properties in the stiffness-matrix, resulting in the LAPACK subroutine returning nonsense.

So it turns out that you can have too many elements in a finite elements method.

2. Small volumes: A few more digits please

Optimized volume in Equation of State fit, as function of the range of the fitting data, and step size between data-points. green diamonds, blue triangles and black discs: 1% , 0.5% and 0.25% volume steps respectively.

Optimized volume in Equation of State fit, as function of the range of the fitting data, and step size between data-points. green diamonds, blue triangles and black discs: 1% , 0.5% and 0.25% volume steps respectively.

Recently, I started working at the Wide Band Gap Materials group at the University of Hasselt. So in addition to MOFs I am also working on diamond based materials. While setting up a series of reference calculations, using scripts which already suited me well during my work on MOFs, I was trying to figure out for which volume range, and step size I would get a sufficient convergence in my Equation-of-States Fitting procedure. For the MOFs this is a computationally rather expensive (and tedious) exercise, which, fortunately, gives clear results. For the 2-atom diamond unit cell the calculations are ridiculously fast (in comparison), but the results were confusing. As you can see in the picture, the values I obtained from the different fits seem to oscillate. Checking my E(V) data showed nothing out of the ordinary. All energies and volumes were clearly distinguishable, with the energies given with a precision of 0.001 meV, and the volumes with a precision of 0.01 Å3. However, as you can see in the figure, the volume-oscillations are of the order of 0.001 Å3, ten times smaller than our input precision. Calculating the volumes based on the lattice parameters to get a precision of 10-6 Å3 for the input volumes stabilizes the convergence behavior of the fits (open symbols in the figure). This problem was not present with the MOFs since these have a unit cell volume which is one hundred times larger, so a precision of 0.01 Å3 makes the relative error on the volumes one hundred times smaller than was the case for diamond.

In essence, I was trying to get more accurate output than the input I provided, which will never give sensible results (even if they actually look sensible).

3. Many grains of sand really start to pile up after a while

The last one is a bit embarrassing as it lead to a bug in the HIVE-toolbox, which is fixed in the mean time.

One of the HIVE-toolbox users informed me that the dosgrabber routine had crashed because it could not find the Fermi-level in the output of a VASP calculation. Although VASP itself gives a value for the Fermi-level, I do not use it in the above sub-program, since this value tend to be incorrect for spin-polarized systems with different minority and majority spins. However, in an attempt to be smart (and efficient) I ended up in trouble. The basic idea behind my Fermi-level search is just running through the entire Density of States-spectrum until you have counted for all the electrons in the system. Because the VASP estimate for the Fermi-level is not that far of, you do not need to run through the entire list of several thousand entries, but you could just take a subset-centered around the estimated Fermi-level and check in that subset, speeding this up by a factor of 10 to 100. Unfortunately I calculated the energy step size between density of states entries as the difference between the first two entries, which are given to with an accuracy of 0.001 eV. I guess you already have a feeling what will be the problem. When the index of the estimated Fermi-level is 1000, the error will be of the order of 1 eV, which is much larger than the range I took into account. Fortunately, the problem is easily solved by calculating the energy step size as the difference between the first and last index, and divide by the number of steps, making the error in the particular case more than a thousand times smaller.

So, trying to be smart, you always need to make sure you really are being smart, and remember that small number can become very big when there are a lot of them. 

May 22 2016

Annual Meeting of the Belgian Physical Society 2016

ConferenceLogoWebsite_1

Wednesday May 18th was a good day for our little family. Since my girlfriend an I both are physicists by training, we attended the annual meeting of the Belgian Physical Society in Ghent, together. What made this event even more special was the fact that both of us had an oral presentation at the same conference, which never happened before. 🙂

Sylvia talked about an example of indeterminism in Newtonian mechanics, and showed how the indeterminism can be clarified by using non-standard analysis. The example considers the Norton Dome, a hill with a specifically designed shape ( y(x)=-2/3(1-(1-3/2|x|)^{2/3})^{3/2} ). When considering a point mass, experiencing only gravitational force, there are two solutions for the equation of motion: (1) the mass is there, and remains there forever (r(t)=0) and (2) the mass was rolling uphill with a non-zero speed which becomes exactly zero at the top, and continues over the top ( r(t)=\frac{1}{144} (t-T)^4 with T the time the top is reached). Here, r refers to the arc length as measured along the dome (0 at the top). In addition, there also exists a family of solutions taking the first solution at t<T, while taking the second solution at t>T. (As the first and second derivatives of these latter solutions are continuous, Newton will not complain.) This leads to indeterminism in a Newtonian system; for instance, you start with a mass on the top of the hill, and at a random point in time it starts to roll off without the presence of an external something putting it into motion. Using infinitesimals, Sylvia shows that the probability for the mass to start rolling off the dome immediately is infinitesimally close to one.

My own talk was on the use of computational materials science as a means for understanding and explaining experimental observations. I presented results on the pressure-induced breathing of the MIL-47(V) MOF, showing how the experimentally observed S-shape of the transition-pressure-curve can be explained by the spin interactions of the unpaired vanadium-d electrons: it turns out that regions with only ferromagnetic chains compress already at 85 MPa, while the addition of higher and higher percentages of anti-ferromagnetic chains increases the pressure at which the pores collapse, up to 125 MPa for the regions containing 100% anti-ferromagnetic chains. As a second topic, I showed how the electronic band structure of the linker-functionalized UiO-66(Zr) MOF changes. When one or two -OH or -SH groups are added to the benzene ring of the linker, part of the valence band is split off and moves into the band gap. In semiconductors, this would be called a gap state; however, in this case, since every linker in the material contributes

Belgian Physical Society Meeting 2016

Top left: I am presenting computational results on MOFs. Top Right: Sylvia presents the Norton Dome. Bottom: Group picture at the central garden in “Het Pand”. (Photos: courtesy of Sylvia Wenmackers (TL), Philippe Smet (TR), and Michael Tytgat (B) )

a single electron state to this gap state, it practically becomes the valence band top. As a consequence, the color of such functionalized MOF’s changes from white to yellow and orange. As a third topic, I discussed the COK-69(Ti) MOF. In this MOF the electrons in the titaniumoxide clusters are strongly correlated, just as for pure titaniumoxide. Because such systems are poorly described with standard DFT, we used the DFT+U approach, which allowed us to discern between Ti3+ and Ti4+ ions. The latter was practically done by partitioning the electron density using the Hirshfeld-I scheme.

Next to our own talks, the BPS-meeting started with two very interesting plenary lectures on the two big machines/facilities of the physics community: ITER (fusion reactor under construction) and LHC (circular collider, under constant upgrade) at CERN. Prof. Jean Jacquinot, presented the progress in fusion research (among which simulations of plasma-instabilities) and the actual building progress of the ITER facility. Prof. Sergio Bertolucci on the other hand informed us on the latest results obtained with the LHC at CERN, but also about future plans (Future Circular Collider, with a circumference of about 100 km!!). He also showed us the amount of data involved in running the CERN experiments, puting them into perspective: LHC produced in 2012 about 15 Petabyte of data per year (15.000 Terabyte) which is the same as the mount of data added to Youtube on yearly basis. At that time the ATLAS experiment had a dataset of 140 Petabyte (compare to the 100 Petabyte of google’s search index or the 180 Petabyte of facebook uploads/year). The presenters, both excellent and enthusiastic speakers, reminded us that these projects thrive on the enthusiasm of young researchers with open minds. But they also noted, something that is rather often forgotten, that it is the journey not the goal which is most important. Of course, ITER is the next step on the road to commercial fusion power, but along the way much more is learned as a result of tackling practical problems. This is even more so for the CERN experiments, where the “goal” is not as related to our daily lives (keeping the lights on) but focuses on understanding the world. This is at the core of what it means to be a physicist: the need and drive to understand the world. This is also what should drive research but becomes increasingly hampered by the funding-question: how/what profit will it make in the “real world”. Remember the transistor which makes your computer and smartphone as powerful as they are, the laser in CD/DVD-players, the internet allowing you to read this post, and so many more.

Following these plenary presentations, four young scientists competed for the young speaker award presenting their PhD research. Two presentations (1),(2) focused on vortices in superconductors, a third one discussed the use of plasmons in graphene nanoribbons to enhance telecommunication while the fourth talk introduced us into the world of string theory.

In the afternoon, there were six parallel session, of which I mainly attended the Condensed Matter and Nanostructure Physics-session (since I had my own talk there) and the Biological, Medical, Statistical and Mathematical Physics-session rooting for Sylvia. During the Condensed matter session I was mainly fascinated by the presentation of Prof. Sara Bals, on coloring atoms in 3 dimensions. She showed how, using energy-dispersive X-ray (EDX) mapping it is possible to create a 3D atomic lattice of nano-materials and clusters. This is a more direct approach than the usual X-ray diffraction (XRD) approach for identifying a crystal structure. Unfortunately, I am afraid this technique may not be well suited for the MOFs I’m working on, since they contain mainly light elements and not heavy metals(although it may be interesting to try once the technique is optimized further). It is, however, definitely a technique to remember for future projects, to suggest to experimental collaborators.

Links:

Apr 12 2016

Call for Abstracts: Condensed Matter Science in Porous Frameworks: On Zeolites, Metal- and Covalent-Organic Frameworks

Flyer for the Colloquium on Porous Frameworks at the CMD26Together with Ionut Tranca (TU Eindhoven, The Netherlands) and Bartłomiej Szyja (Wrocław University of Technology, Poland) I am organizing a colloquium “Condensed Matter Science in Porous Frameworks: On Zeolites, Metal- and Covalent-Organic Frameworks” which will take place during the 26th biannual Conference & Exhibition CMD26 – Condensed Matter in Groningen (September 4th – 9th, 2016). During our colloquium, we hope to bring together experimental and theoretical researchers working in the field of porous frameworks, providing them the opportunity to present and discuss their latest work and discoveries.

Zeolites, Metal-Organic Frameworks, and Covalent-Organic Frameworks are an interesting class of hybrid materials. They are situated at the boundary of research fields, with properties akin to both molecules and solids. In addition, their porosity puts them at the boundary between surfaces and bulk materials, while their modular nature provides a wealthy playground for materials design.

We invite you to submit your abstract for oral or poster contributions to our colloquium. Poster contributions participate in a Best Poster Prize competition.

The deadline for abstract submission is April 30th, 2016.

The extended deadline for abstract submission is May 14th, 2016.

 

CMD26 – Condensed Matter in Groningen is an international conference, organized by the Condensed Matter Division of the European Physical Society, covering all aspects of condensed matter physics, including soft condensed matter, biophysics, materials science, quantum physics and quantum simulators, low temperature physics, quantum fluids, strongly correlated materials, semiconductor physics, magnetism, surface and interface physics, electronic, optical and structural properties of materials. The scientific programme will consist of a series of plenary and semi-plenary talks and Mini-colloquia. Within each Mini-colloquium, there will be invited lectures, oral contributions and posters.

 

Feel free to distribute this call for abstracts and our flyer and we hope to see you in Groningen!

Apr 06 2016

Animated Primes

Optimus Prime

Optimus Prime, the most prime of all autobots.[source]

2, 3, 5, 7, 11, 13, 17, 19, 23, …and on toward infinity. Prime numbers are a part of mathematics which seduce most of us at some point in our lives to try and “solve them”. There is structure in them, but too little to be easily understandable, and too much to let go and consider them chaos.

Recently, my girlfriend got sucked into this madness. Luckily she is not trying to generate the next largest prime (which would need to have more than 22 Million digits, although I might have jinxed it now). Instead she is looking for order into chaos; leading to pen and paper graphs, evolving into excel worksheets being abused as ordinary bitmap pictures and finally mathematica applications for even more heavy lifting.

These last exercises came to a somewhat grinding halt when mathematica refused to generate a gif-animation (it just failed to do the job without providing any warning that something might have gone awry). However, because it could generate the separate frames without any issues, I was tempted to dig up an old fortran module which allowed me to generate gif images and animations. I remembered correctly that it was able to both read and write gif-images, and so, after 10 minutes of writing a small program (9 minutes remembering how things worked) and another 10 linking in all dependencies and fixing some inconsistencies, I had a working program for generating a gif animation from separate gif images.

Animated gif, generated in fortran.

The initial test went smoothly. Using some simple gif images I created in paint, the resulting 4 frame animation is the one on the left (which is probably giving you a headache as you read this ;-).

The real test, with the single frame gifs Sylvia had prepared, was rather interesting: It failed miserably. Fortunately it also taught us the origin of the problem: mathematica was generating frames of different dimensions. And although this does not give rise to problems in the workbook or generated avi, it does kill an animated gif. After fixing this, also mathematica successfully generated the animated gif Sylvia wanted to see. Also my own small program was now able to perform the intended trick, although it showed that a different color-map was created for each frame by mathematica, something my own implementation did not handle well (we’ll fix that somewhere in the future).

The executable (including prerequisite dll’s) can be downloaded here.

If you do not suffer from epileptic seizures (or not yet), you could check out the results in the spoiler below.

Spoiler Inside: gif-animations SelectShow

Mar 09 2016

SBDD XXI

SBDD XXI logoToday was the first day of the three-day long diamond conference at the university of Hasselt. And although this sounds as-if it is a mere small-scale local conference, it is actually one of the two main international conferences in the field. The Surface and Bulk Defects in Diamond (SBDD) workshop grew in twenty years from a small event with only a few dozen participants to the current event with over 200 participants. As such, it is the place to be, for one as me, who is dipping into a new field of materials.

One thing that already became quite clear today, is the fact that there are many opportunities in this field for the computational materials scientist, as the large majority of the researchers are experimentalists. Of the >120 posters presented, I have only discovered about 5 theoretical ones. Having had very nice chats with their presenters I already learned a lot of what I will have to keep in mind when studying diamond. But so far, I have not come across any issues that are impossible to resolve, which is good news :-).

Mar 08 2016

New sidekick

“One ring to rule them all, one ring to find them, one ring to bring them all, and in the darkness bind them” – J.R.R. Tolkien

“One ring to rule them all, one ring to find them, one ring to bring them all, and in the darkness bind them” – J.R.R. Tolkien

With the start of my new chapter, I also decided to finally buy a new laptop. It’s intended to replace the machine I used at work for the past six years, my desktop at home and my current little netbook. Of these the latter has been my true sidekick for the better part of the last decade. Although nearly all my calculations have been performed on various supercomputers in Belgium and The Netherlands, my little Asus Eee-pc 1000H, being one of the last vestiges of windows XP, was the one which I used to write nearly all of my publications, a PhD in Physics and in Chemistry, my FWO project proposal on MOFs, developed most of the HIVE toolbox, wrote the better part of this blog and website, developed and tested the agent-tutorials, and much more. In short, I did (and still do) protect it with my life.

With the unfortunate and in the end terminal shutdown of WIn XP (i.e. some people discovered how to detect the OS and link this to a kill event…just because XP no longer receives updates, and therefore suddenly becomes as leaky as a sieve 🙄 ) a new OS was needed. In addition, I also wanted some more resources for development (and just running a browser…It feels like programming skills are quickly deteriorating these days if you see how memory intensive even trivial applications are), so the new OS ended up being a new computer altogether. After some searching, I found the laptop which I hope to be using for the next decade: an Acer Predator 15. It has a nice intel skylake cpu (dual-threaded quad-core with 6Mb L3 cache, the 8Mb version was not to be found with the 32Gb of RAM I was looking for). The contrast with my netbook could not be greater, so I’ll be checking and comparing performance of my HIVE-code on this new machine to that on my old Asus netbook (dual-threaded atom cpu, with 1Gb of RAM) . This should give some interesting results.

Not having installed a new windows OS since 2007, windows 10 came as quite a shock (and the aftershocks are still coming.) It seems like privacy is a thing of the past. Anything you say, watch, type, draw is by default send to the home office, and distributed to third parties which may be interested in providing you “user specific content” (i.e. commercials 😥 ) This is in stark contrast to the days where people often installed several antivirus programs and firewalls to protect their data from hackers…now we just seem to throw that same information out for grabs. Then to say there are people who believe we are on the verge of the end of capitalism. I’m afraid they either are misreading the signs, or some are reading the signs very accurately and are collecting the new gold before it has been declared gold. I feel like I’m getting old, or just old-school.

One of the advantages of having lived through those early years where fear of internet-hackers and piracy were defaults, is that we also learned to get around all the same protections. Maybe you remember the irony of having to rip a CD to be able to simply listen to it because of all protection-software (and hardware when you rented it at the local library)? It seems those days are back. While installing some old games, I ran into a piracy-protection software (which is no longer supported due to security leaks) which blocked both playing and even installing the game. So you end up either buying the game through steam (as many will suggest you…why should I do that if I bought the game already…twice?) or installing it on an older machine, just brute-force copying the entire installed game, copying/installing missing dll’s and finding a no-cd crack (Yes, it is claimed as illegal, but since most machines these days come without optical drives I beg to differ), or figure out another way to play old games. In the end, you start with a feeling of victory before even playing a new round of Civilizations 4…which is nice and sad at the same time (it should not have been necessary).

Another interesting experience was the transfer of my emails from my UGent address to the UHasselt one. Mail-clients like Outlook and Thunderbird seem not that well adapted to easily handle such exercises (missing folders and emails upon copy-actions, which needed to be fixed manually), especially if you have a very extensive folder-structure. The most nasty problem I encountered when setting up accounts was the fact that the new UHasselt (gmail) account could not be linked to the thunderbird installation (even though the intermediate gmail-account for transferring my UGent mail was not that problematic). Apparently there was also a cookies option embedded in thunderbird itself, which should be switched on, woeps.

Two weeks after the start of my new chapter, most hurdles have been overcome. Nearly all necessary software has been installed (with or without the cooperation of the windows 10 OS  👿 ), my e-mail has been transferred, as well as 4Tb of data on the HPC systems (for which I am infinitely grateful to both the HPC teams of the UGent and UHasselt). Now it is time to start working again. Tomorrow, the diamond conference starts at the UHasselt, giving me the opportunity to quickly get involved in a new, additional field of materials.

 

Mar 01 2016

Helium flash: the beginning of a new chapter.

During the past two and a half years, part of being a delocalized physicist has meant for me that I had to work at one end of the country while my girlfriend and son lived at the other. Today this situation drastically changed, as I moved with my FWO-postdoctoral project from my alma mater to the University of Hasselt, where I started in the Wide Band Gap Materials group of Prof. Ken Haenen.

My delocalization will now take the form of Metal-Organic Frameworks on the one side and Diamond based materials on the other. As the sole computational solid state physicist in an otherwise entirely experimental group (and even institute) I seem to have returned to a well known configuration (At Ghent university I was initially the house-theoretician of the SCRiPTS group). Also the idea of performing calculations on diamond brings back memories, since this allotrope of carbon lives two levels above the germanium on which Pt nanowires grow. All-in-all I look forward to an exciting time. But first things first: getting my HPC credentials and data safely transported from the one end of the country to the other.

Feb 04 2016

Virtual Winterschool 2016: Computational Solid State Physics & Chemistry

In just an hour, I’ll be presenting my talk at the virtual winterschool 2016. In an attempt to tempt fate as much as possible I will try to give/run real-time examples on our HPC in Gent, however at this moment no nodes are available yet to do so. Let’s keep our fingers crossed and see if it all works out.

Abstract

Modern materials research has evolved to the point where it is now common practice to manipulate materials at nanometer scale or even at the atomic scale (e.g. Intel’s skylake architecture with 14nm features, atomic layer deposition and surface structure manipulations with an STM-tip). At these scales, quantum mechanical effects become ever more relevant, making their prediction important for the field of materials science.

In this session, we will discuss how advanced quantum mechanical calculations can be performed for solids and indicate some differences with standard quantum chemical approaches. We will touch upon the relevant concepts for performing such calculations (plane-wave basis-sets, pseudo-potentials, periodic boundary conditions,…) and show how the basic calculations are performed with the VASP-code. You will familiarize yourself with the required input files and we will discuss several of the most important output-files and the data they contain.

At the end of this session you should be able to set up a single-point calculation, a structure optimization, a density of states and band structure calculation.

Additional Files/Info

Jan 29 2016

Winterschool on computational chemistry

Starting next week from February 3rd up to February 9th the second virtual winterschool on computational chemistry will take place. This week-long winter school is packed with interesting webinars given by experts from all over the world (among others Kieron Burke and John Perdew, jep those of the DFT-functionals we are using) and me. I’ll be presenting an introductory tutorial in solid state calculations and how to use VASP for this task.

Registration for this winter school is free, and since it takes place on the world wide web, there is still room at the back :-). (In addition to a lack of worries whether or not you will be able to get your hands on a last minute plane-ticket or hotel-room and which funding agency might reimburse those tickets.) I’ll be running example-calculations real time, and hope my sidekick will perform to expectation.

Jan 01 2016

Review of 2015

With 2015 having past on moving quickly toward oblivion, and 2016 freshly knocking at our door, it is time to look back and contemplate what we have done over the course of the previous year.

Publications: +5

 

Journal covers:+1Cover image CrystEngComm 2015 Vol 17 Issue 45

 

Completed refereeing tasks: +11

  • ACS Catalysis
  • Frontiers in Physics (2x)
  • Journal of Physics: Condensed Matter
  • Proceedings for 39th International Conference & Exposition on Advanced Ceramics & Composites
  • Applied Physics Letters (2x)
  • Materials Science in Semiconductor Processing
  • Journal of Superconductivity and Novel Magnetism (2x)
  • Surface Science

 

Conferences: +3 (Attended) & + 1 (Organized)

 

Master-students: +1

  • Arthur De Vos : Combined theoretical-experimental study of chromium doped zinc gallate phosphor

 

Jury member of PhD-thesis committee: +1

  • Ir. Yuanyuan Guan
    Title: Development of a method to determine the solubility ranges of intermetallic compounds in metal-metal connections
    PhD candidate at KU Leuven with Prof. Dr. Ir. Nele Moelans
    Department of Materials Engineering

Current size of HIVE:

  • 44K lines of program (code: 71 %)
  • 64 files
  • 40 (command line) options

Hive-STM program:

 

And now, upward and onward, a new year, a fresh start.