Predicting morphotropic phase boundary locations and transition temperatures in Pb- and Bi-based perovskite solid solutions from crystal chemical data and first-principles calculations

Using data obtained from first-principles calculations, we show that the position of the morphotropic phase boundary (MPB) and transition temperature at MPB in ferroelectric perovskite solutions can be predicted with quantitative accuracy from the properties of the constituent cations. We find that the mole fraction of PbTiO$_3$ at MPB in Pb(B$'$B$''$)O$_3$-PbTiO$_3$, BiBO$_3$-PbTiO$_3$ and Bi(B$'$B$''$)O$_3$-PbTiO$_3$ exhibits a linear dependence on the ionic size (tolerance factor) and the ionic displacements of the B-cations as found by density functional theory calculations. This dependence is due to competition between the local repulsion and A-cation displacement alignment interactions. Inclusion of first-principles displacement data also allows accurate prediction of transiton temperatures at the MPB. The obtained structure-property correlations are used to predict morphotropic phase boundaries and transition temperatures in as yet unsynthesized solid solutions.Comment: Accepted for publication in J. Appl. Phy

Variabilitas Harian Komunitas Ikan Padang Lamun Perairan Tanjung Tiram-Teluk Ambon dalam [Daily Variability Of Fish Community In Sea Grass Beds Of Tanjung Tiram-Inner Ambon Bay]

Penelitian ini dilaksanakan di perairan Tanjung Tiram , Teluk Ambon Dalam selama bulan Juli-Agustus 2012, untuk membandingkan kelimpahan dan struktur komunitas ikan padang lamun berdasarkan perbedaan siang dan malam hari. Ikan dikoleksi dengan metode sapuan menggunakan pukat pantai yang ditarik pada hamparan padang lamun sebanyak enam kali (masing-masing tiga kali mewakili siang dan malam hari). Hasil penelitian mendapatkan total jumlah individu ikan sebanyak 5593 individu dari 72 spesies dan 35 famili. Siganus canaliculatus mendominasi struktur komunitas ikan baik pada siang maupun malam hari, Ostorhinchus lateralis aktif pada malam hari, dan Aeoliscus strigatus yang aktif pada siang hari. Terdapat variasi struktur komunitas ikan antara siang dan malam, dengan nilai dominansi selalu lebih tinggi pada malam hari. Sebaliknya, keanekaragaman selalu tinggi pada siang hari dan keseragaman spesies lebih stabil pada siang hari. Variabilitas kelimpahan dan struktur komunitas ikan antara siang dan malam hari selain berkaitan dengan sifat nokturnal dan diurnal, juga dipengaruhi fluktuasi parameter oseanografi. Suhu, salinitas, oksigen terlarut, dan pH berpengaruh positif, sedangkan kekeruhan perairan berpengaruh negatif terhadap kelimpahan ikan di ekosistem padang lamun

A More Accurate Generalized Gradient Approximation for Solids

We present a new nonempirical density functional generalized gradient approximation (GGA) that gives significant improvements for lattice constants, crystal structures, and metal surface energies over the most popular Perdew-Burke-Ernzerhof (PBE) GGA. The new functional is based on a diffuse radial cutoff for the exchange-hole in real space, and the analytic gradient expansion of the exchange energy for small gradients. There are no adjustable parameters, the constraining conditions of PBE are maintained, and the functional is easily implemented in existing codes.Comment: 5 pages, corrected the errors of the sublimation energy of Ih ic

Growth Rate, Cover, and Survival Rate (Enhalus Acoroides) Transplanted in Monospecies and Multispecies

One of seagrass dominant species found in Indonesia is Enhalus acoroides. This species can form single seagrass bed vegetation (monospecies vegetation) and mixed with others species (multispecies vegetation). Seagrass composition in coastal areas can be affected by surrounding associated species such as herbivorous fish and invertebrates. Human activities, especially in coastal communities, can negatively influence seagrass beds. Therefore, it is needed an effort to rehabilitate the affected seagrass. Transplantation technic is one effort for rehabilitation. The purposes of the research were to analyze growth rate, percent cover, and survival rates of seagrass E. acoroides transplanted as monospecies and multispecies. This research used a monospecies of E. acoroides and multispecies (2, 4, and 5 species) that combined to others species such as T. hemprichii, C. rotundata, H. ovalis, H. uninervis, and S. isoetifolium. Research results showed that the highest average growth rate of transplanted E. acoroides was found in monospecies treatment with 0.29 cm/day. The highest average cover changing was found on two combined species i.e., E. acoroides and C. rotundata, as high as 0.10% per day. The highest survival rates were found in 2 combined treatment i.e., E. acoroides and H. ovalis, and 5 combined species such as E. acoroides, S. isoetifolium, C. rotundata, H. uninervis dan H. ovalis with value 100 percent, respectively

Structure and Vibrations of the Vicinal Copper (211) Surface

We report a first principles theoretical study of the surface relaxation and lattice dynamics of the Cu(211) surface using the plane wave pseudopotential method. We find large atomic relaxations for the first several atomic layers near the step edges on this surface, and a substantial step-induced renormalization of the surface harmonic force constants. We use the results to study the harmonic fluctuations around the equilibrium structure and find three new step-derived features in the zone center vibrational spectrum. Comparison of these results with previous theoretical work and weith experimental studies using inelastic He scattering are reported.Comment: 6 Pages RevTex, 7 Figures in Postscrip

The Composition of Species and Structure of Seagrass Fish Community in Tanjung Tiram – Inner Ambon Bay

The study was conducted in March - May 2011 in the coastal waters of Tanjung Tiram – inner Ambon bay. The aims of the study were to determine the composition of species and structure of fish communities in seagrass beds ecosystems. Fish were collected every spring and neap tide for three month periode with a swept area method using beach seine. Fishes were collected as many as 6444 individuals representing 68 species from 29 families. Siganus canaliculatus was contributed up to 62.91% of the total individual fish found.The fish community structure was varied between spring and neap tide. Index of dominance was in low category, diversity in medium, and evenness in unstable conditions. Moreover, the results indicated that seagrass ecosystems in Tanjung Tiram (TAD) have an important role as spawning, nursery ground, and feeding ground. Therefore, management and conservation efforts are urgently needed to maintain the ecological role of seagrass ecosystems for the sustainability of the fish resources

Structure and dielectric response in the high TcT_c ferroelectric Bi(Zn,Ti)O3_3-PbTiO3_3 solid solutions

Theoretical {\em ab initio} and experimental methods were used to investigate the $x$Bi(Zn,Ti)O$_3$-(1-$x$)PbTiO$_3$ (BZT-PT) solid solution. We find that hybridization between Zn 4$p$ and O 2$p$ orbitals allows the formation of short, covalent Zn-O bonds, enabling favorable coupling between A-site and B-site displacements. This leads to large polarization, strong tetragonality and an elevated ferroelectric to paraelectric phase transition temperature. nhomogeneities in local structure near the 90$^\circ$ domain boundaries can be deduced from the asymetric peak broadening in the neutron and x-ray diffraction spectra. These extrinsic effects make the ferroelectric to paraelectric phase transition diffuse in BZT-PT solid solutions