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All Journal Jurnal Ilmu Dasar Journal of Mathematical and Fundamental Sciences Journal of Engineering and Technological Sciences Jurnal Kimia Mulawarman Jurnal Riset Sains dan Kimia Terapan Indonesian Journal of Physics (IJP)
Hermawan K. Dipojono
Advanced Functional Materials Research Group, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia
Astronomy Chemistry Computer Science & IT Control & Systems Engineering Earth & Planetary Sciences Electrical & Electronics Engineering Energy Engineering Mathematics Physics

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Theoretical Study of Direct Carbon Dioxide Conversion to Formic Acid on Transition Metal-doped Subnanometer Palladium Clusters Adhitya Gandaryus Saputro; Arifin Luthfi Maulana; Fine Dwinita Aprilyanti; Hermawan Kresno Dipojono
Journal of Engineering and Technological Sciences Vol. 53 No. 4 (2021)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2021.53.4.2

Abstract

We studied the direct conversion of CO2 to HCOOH through hydrogenation reaction without the presence of base additives on the transition metal-doped subnanometer palladium (Pd7) cluster (PdxM: M = Cu, Ni, Rh) by using a combination of density functional theory and microkinetic calculations. It was shown that the CO2 hydrogenation on Pd7 and Pd6M clusters are more selective towards the formate pathway to produce HCOOH than the reverse water gas shift pathway to produce CO. Inclusion of Ni and Rh doping in the subnanometer Pd7 cluster could successfully enhance the turnover frequency (TOF) for CO2 hydrogenation to formic acid at low temperature. The order of TOF for formic acid formation is as follows: Pd6Ni > Pd6Rh > Pd7 > Pd6Cu. This order can be explained by the trend of the activation energy of CO2 hydrogenation to formate (HCOO*). The Pd6Ni cluster has the highest TOF value because it has the lowest activation energy for the formate formation reaction. The Pd6Ni system also has a superior TOF profile for HCOOH formation compared to several metal surfaces in low and high-temperature regions. This finding suggests that the subnanometer PdxNi cluster is a promising catalyst candidate for direct CO2 hydrogenation to formic acid.
STUDI AB INITIO GRAFIT BATUBARA SEBAGAI MATERI PENYIMPAN HIDROGEN Rahmat Gunawan; Melanie David; Hideaki Kasai; Muhammad A. Martoprawiro; Cynthia L. Radiman; Herman K. Dipojono
JURNAL KIMIA MULAWARMAN Vol 8 No 1 (2010)
Publisher : Jurusan Kimia Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Mulawarman

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Abstract

Calculation of density functional theory (DFT) is carried out to investigate the adsorption of six molecules of H2 molecules on a graphite planar layer with a doping of alkali metal (Li, Na, and K). We reported that the DFT-GGA method, the presence of alkali metals on graphite, and H2-(GICs), have changed the interaction and the electronic system. We also reported that the ratio increased electron transfer from K to Na and Li. The calculation of the charge density shows that the increase in energy due to the transfer of electrical charge from GICs to six molecules of H2. This changes the electronic properties of graphite that are important in applications such as hydrogen storage.Keywords: Molecule Hydrogen, Graphite Intercalated Compounds, Density Functional Theory
Immobilization of Amino Acids Leucine and Glycine on Polypyrrole for Biosensor Applications: A Density Functional Theory Study Hermawan K. Dipojono; Irna Safitri; Nugraha Nugraha; Eko Mursito Budi; Nuryanti Nuryanti; Adhitya G. Saputro; Melanie Y. David; Hideaki Kasai
Journal of Mathematical and Fundamental Sciences Vol. 43 No. 2 (2011)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2011.43.2.4

Abstract

Adsorption based on the immobilization of amino acids, i.e. leucine and glycine, on the surface of undoped polypyrrole (Ppy) is investigated. Calculations are done based on density functional theory using Gaussian03 software and applying GGA with 6-31G(d) basis set and exchange-correlation model of PBE (Perdew, Burke, Ernzerhof) level of theory. The energy of the Ppy doped with amino acids are minimized with respect to the orientation and distance of the amino acids to the Ppy. Neutral leucine carboxyl shows greater binding energy as compared to that other leucine configurations. It has adsorption energy of 0.25 eV at optimum distance of 2.2 Ã… from the surface of Ppy. As for the glycine, the zwitterionic carboxyl exhibits the strongest binding energy among other glycine configurations. It has adsorption energy of 0.76 eV at optimum distance of 1.7 Ã… from the surface of Ppy. The adsorption processes for both amino acids should proceed easily because the activation barriers are either absent or very small.
On Non-Linear Finite State Digital Channel Coding Hermawan Kresno Dipojono
Journal of Mathematical and Fundamental Sciences Vol. 20 No. 1/2 (1987)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract

Abstract. A discrete-time digital channel coding, in which the encoder and decoder are both time-invariant finite state machines, is investigated. The channel is assumed to be memoryless. Two measures of performance are considered: the probability of error and the minimum free distance. Greater emphasis is placed on the minimum free distance since it is easier to evaluate than the probability of error criterion, and for small channel crossover probability it is a very good indicator of system performance; it is defined as the Hamming distance between two possible output sequences that correspond to distinct state sequences of the same length that are identical at both the start and finish. An algorithm to calculate the distance between such possible output sequences was developed; it also identifies all such pain of output sequence. Another algorithm, based on the finite state machine properties of the encoder, was found to generate the finite state decoder. Finally, after having found the pairs of encoder-decoder finite state machines, we simulated the communication system. Sari. Suatu kode saluran digital dengan waktu tercacah yang mempunyai pasangan encoder-decoder berupa mesin berkeadaan terhingga dan invarian waktu akan diteliti. Saluran dianggap tanpa daya ingat. Digunakan dua buah ukuran kinerja yaitu probabilitas kesalahan dan jarak bebas minimum. Penggunaan jarak bebas minimum lebih ditekankan karena lebih mudah dievaluasi dibandingkan probabilitas kesalahan. Untuk probabilitas kesalahan saluran yang kecil, jarak itu merupakan indikator yang sangat baik bagi kinerja sistem; ia didefinisikan sebagai jarak Hamming minimum antara dua buah kemungkinan sekuen keluaran yang berupa sekuen keadaan yang unik dengan panjang dan keadaan yang sama, baik di awal maupun di akhir sekuen. Sebuah algoritma untuk menghitung jarak antara sekuen keluaran yang sedemikian itu telah pula dikembangkan; algoritma tersebut juga mampu mengidentifikasi semua pasangan sekuen keluaran itu. Sebuah algoritma lainnya, didasarkan pada sifat-sifat encoder sebagai mesin dengan keadaan berhingga, yang mampu menyusun decoder dengan keadaan berhingga, telah pula ditemukan. Akhirnya, setelah menemukan berbagai pasangan encoder-decoder yang berupa mesin dengan keadaan berhingga, sistem komunikasi digital disimulasikan.
PERMUKAAN ENERGI POTENSIAL HIDROGEN PADA SISTEM GRAFIT TERINTERKALASI INVESTIGASI TEORI FUNGSI KERAPATAN Rahmat Gunawan; Melanie David; Hideaki Kasai; Muhamad A. Martoprawiro; Cynthia L. Radiman; Hermawan K. Dipojono
Jurnal Riset Sains dan Kimia Terapan Vol 1 No 2 (2011): JRSKT - Jurnal Riset Sains dan Kimia Terapan, Volume 1 Nomor 2 Desember 2011
Publisher : Program Studi Kimia Universitas Negeri Jakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3093.794 KB) | DOI: 10.21009/JRSKT.012.01

Abstract

Permukaan energi potensial untuk sistem hidrogen pada permukaan grafit terinterkalasi alkali (Li, Na dan K) telah diteliti, secara teoritis. Model struktural, sifat energik, dan elektronik dari hidrogen pada sistem alkali/grafit dihitung melalui teori fungsi kerapatan (DFT) dengan menggunakan pendekatan koreksi gradien Perdew-Burke-Ernzerhof (PBE). Perhitungan dilakukan dengan menggunakan basis set plane-wave, dan interaksi elektron-inti dijelaskan menggunakan pendekatan pseudopotential. Pada langkah pertama, permukaan energi potensial diperoleh dengan cara menghitung energi berbagai posisi molekul hidrogen pada permukaan grafit, yaitu di atas atom karbon (top), di atas ikatan C=C (bridge), dan di atas ring (hollow). Diperoleh hasil bahwa molekul hidrogen yang paling stabil adalah pada posisi top, dengan energi sebesar 3,2 eV pada jarak 0,019 A. Selanjutnya semua perhitungan dilakukan pada jarak 3,2 A dari permukaan grafit. Pada langkah berikutnya, permukaan energi potensial atom alkali (Li, Na, dan K) pada permukaan grafit memberi hasil bahwa atom alkali paling stabil pada posisi hollow dengan jarak antara Li, Na, dan K pada permukaan grafit adalah 1,7 A, 2,3 A, dan 2,6 A dengan energi minimum -1,37 eV, -0,66 eV dan -0,96 eV, secara berurutan. Dari data kerapatan muatan menunjukkan bahwa terjadi peningkatan transfer muatan elektron dari atom alkali terhadap orbital elektron pi grafit. Pada langkah terakhir, permukaan energi potensial minimum diperoleh pada variasi posisi hidrogen molekul pada sistem grafit terinterkalasi atom alkali, dan menunjukkan model permukaan energi potensial seperti yang ditunjukkan pada gambar di bawah. Diperoleh bahwa terdapat enam titik energi potensial terendah yang dapat ditempati oleh enem molekul hidrogen yaitu pada posisi bridge dari sistem ini. Jarak antara keenam molekul hidrogen dengan atom Li, Na, dan atom K adalah 2,6 A, 2,7 A, dan 2,8 A, dengan energi minimum -0,082 eV, eV dan -0,071 -0,079 eV, secara berurutan. Hal ini menunjukkan bahwa kehadiran atom Li memberikan nilai kapasitas yang lebih tinggi dibandingkan dengan atom Na dan K. Hasil ini mendukung dan menjelaskan secara kualitatif adanya peningkatan kapasitas penyimpanan hidrogen dalam sistem alkali-grafit. kata kunci : Teori fungsi kerapatan, hidrogen, grafit terinterkalasi atom alkali
Oxygen Reduction Reaction Mechanism on the Square Paddle-Wheel Cage Site of TM-BTC (TM=Mn, Fe, Cu) Metal-Organic Framework Ahmad Nuruddin; Adhitya Gandaryus Saputro; Syauqi Abdurrahman Abrori; Arifin Luthfi Maulana; Virgiawan Listanto Rahagung; Mohammad Kemal Agusta; Fadjar Fathurrahman; Amrina Mustaqim; Hermawan Kresno Dipojono
Journal of Mathematical and Fundamental Sciences Vol. 54 No. 2 (2022)
Publisher : Directorate for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2022.54.2.2

Abstract

Our study examined the mechanism of oxygen reduction reactions (ORR) at the square paddle-wheel cage active site of TM-BTC metal-organic frameworks (MOFs), where TM is a transition metal, Mn, Fe, or Cu. We used a combination of density functional theory (DFT) and microkinetic calculations to investigate this mechanism. By using a small cluster for modeling the TM-BTC active site structure, we successfully reproduced the experimental trend of ORR activity in the TM-BTC systems: Mn-BTC > Fe-BTC > Cu-BTC. We also found that the unusual ORR activity trend in experiments for Mn and Fe systems originates from the strength of OH adsorption on these systems. The Mn-BTC system exhibits higher ORR activity than the Fe-BTC system due to its weaker adsorption of OH groups. A very strong OH adsorption makes the final OH reduction step sluggish, hence hindering the ORR process.
Ab initio Computation Revisited: Fweb Based Code for Educational Purposes Hermawan K. Dipojono
Indonesian Journal of Physics Vol 15 No 1 (2004): Vol. 15 No.1, January 2004
Publisher : Institut Teknologi Bandung

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Abstract

We present an fweb based ab initio computation for educational purposes. As such we emphasized more on simplicity but without loss of generality and on readability than on efficiency of the code for this nontrivial problem. In order to check that our code worked we have tested the code to evaluate the total energies for some elements. We used our code to evaluate the total energies of hydrogen, carbon, oxygen atoms and O+. The total energies from our computation were compared to the available data from US National Institute of Standard and Technology (NIST). The results showed that our fweb based ab initio code has performed excellently. For the development of the code we used the density functional theory with local density approximation which gave a relatively simple but accurate prescription for the total energy of a system of electrons and nuclei. The rate of convergence to the final total energy will be presented in terms of total energy versus number of iterations with mixing factor α as a parameter. In the sense of self-consistent computation α is a measure of mixing between the previous and the new density value in order to get the density value for the next step computation in the iteration. Our computation shows that α = 0.55 gives the best performance.
Preliminary Study of Steels Corrosion Phenomena in Liquid Lead-Bismuth using Molecular Dynamics Methods Alan Maulana; Zaki Su'ud; Hermawan K. Dipojono; Khairurrijal Khairurrijal
Indonesian Journal of Physics Vol 18 No 1 (2007): Vol. 18 No. 1, January 2007
Publisher : Institut Teknologi Bandung

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Abstract

One of the prospective coolant material which can be used in the forth generation nuclear reactor is a liquid lead-bismuth. This coolant has inherent safety capability, economical, and able to burn their own nuclear waste. The problem of using this coolant is corrosion phenomena of steel occurred in the interaction with liquid lead-bismuth especially at high temperatures. Corrosion in this study is assumed as diffusion phenomena of leads or bismuths into the surface of steel. This phenomenon have been studied by molecular dynamic methods. As the first step to this investigation, the molecular dynamic program called Moldy has been used to simulate pure iron and lead system. The molecular dynamic simulation result of pure Fe system at 0 K showed that the peaks positions of radial distribution function is in a good agreement with the result from experiment. The deviation of the peaks position resulted from simulation and experiment is about 0.5%. The simulation result of Pb system showed no significant different with the result from experiment. The simulation also shows the broadening of the curves of radial distribution function and lowering the intensity at high temperature. These results indicate that the atomic positions of the system are distributed randomly.
Corrosion Study of Steels In Liquid Lead-Bismuth Cooled Nuclear Reactors by Computer Simulation using Moldy Code Alan Maulana; Zaki Su'ud; Hermawan K. Dipojono; Khairurrijal Khairurrijal
Indonesian Journal of Physics Vol 18 No 2 (2007): Vol. 18 No. 2 April 2007
Publisher : Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (493.065 KB) | DOI: 10.5614/itb.ijp.2007.18.2.3

Abstract

The corrosion of steel in liquid lead-bismuth has been studied by computer simulation using MOLDY code. The diffusion processes among atoms are assumed to be the key issues to understand the corrosion mechanism microscopically. In order to simulate these diffusion processes, the inter-atomic potential between Fe-Fe, Pb-Pb, Bi-Bi, Cr-Cr and Ni-Ni are assumed to obey the Lennard-Jones potential. The Lennard-Jones potential parameters of above pairs of atom have been derived by fitting the data available in the literature with the Lennard-Jones equation. The initial positions of the system are taken from the crystal structures data including the cell parameters. The simulation cell was a box with the volume 60x30x30 Å3 that were filled by 2864 atoms. Nickel and chromium atoms were substituted into Fe crystal with the percentage 10% and 16 % respectively to construct the systems of SS-316 which contacted by 50%Pb-50%Bi. The molecular dynamic simulations have been carried out for surface interaction between steel crystal with liquid lead-bismuth for several temperatures. After done the above simulation, the simulation is then tried by using 45%Pb-55%Bi (Pb-Bi Eutectic). The results of molecular dynamic simulations for several temperatures and the effect of variation of Pb and Bi above will be presented in this paper.
Graphite as A Hydrogen Storage in Fuel Cell System: Computational Material Study for Renewable Energy Gunawan, Rahmat; Radiman, Cynthia Linaya; Martoprawiro, Muhamad Abdulkadir; Dipojono, Hermawan K.
Jurnal ILMU DASAR Vol 17 No 2 (2016)
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (376.871 KB) | DOI: 10.19184/jid.v17i2.3499

Abstract

The Hydrogen storage based-graphite materials have been investigated theoretically via Density Functional Theory (DFT) approach. The native graphite was compared to the modified graphite, namely the intercalation graphite (GICs, graphite intercalated compounds). Here the GICs was intercalated by alkali metals (Li, Na and K). The electronic structures, energetics and atomic orbital contributions of hydrogen-graphite system, GICs, and hydrogen-GICs were studied by calculation approach of gradient corrected PBE (Perdew-Burke-Ernzerhof) for recovery of exchange-correlation energy. The calculation was supported by using basis set of the plane waves whereas the computation of electron-core by using Ultrasoft Vanderbilt pseudopotential. The computational calculation provides four main studies i.e. molecular geometry relaxation, determination of electronic bands structure of energy, energy state density (DOS) and atomic orbital contribution by charge density differences.Keywords: Density Functional Theory, hydrogen gas, graphite intercalated material
Co-Authors Adhitya G. Saputro Adhitya Gandaryus Saputro Ahmad Nuruddin Alan Maulana Alan Maulana Amrina Mustaqim Arifin Luthfi Maulana Arifin Luthfi Maulana Cynthia L. Radiman Cynthia L. Radiman Cynthia Linaya Radiman Eko Mursito Budi Fadjar Fathurrahman Fine Dwinita Aprilyanti Hideaki Kasai Hideaki Kasai Hideaki Kasai Irna Safitri Khairurrijal Khairurrijal Melanie David Melanie David Melanie Y. David Mohammad Kemal Agusta Muhamad A. Martoprawiro Muhamad Abdulkadir Martoprawiro Muhammad A. Martoprawiro Nugraha Nugraha Nuryanti Nuryanti Rahmat Gunawan RAHMAT GUNAWAN Rahmat Gunawan Syauqi Abdurrahman Abrori Virgiawan Listanto Rahagung Zaki Suud