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Study of Anharmonic Effects in the Presence of Adparticles at the Surfaces of Crystals of Noble Metals

Thesis Info

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Author

Shah, Zulfiqar Ali

Program

PhD

Institute

Hazara University

City

Mansehra

Province

KPK

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/6671/1/Zulfiqar_Ali_Shah_Physics_Hazara_Univ_2015.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727364529

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The anharmonic effects at/near the surfaces of noble metals in the presence of adparticles have been presented at 300, 500 and 700 K temperatures. The Molecular Dynamics (MD) simulations are carried out for Cu(111), Cu(311), Cu(210) and Ag(111) surfaces using realistic many-body interatomic potentials obtained from the Embedded Atom Methods (EAM). In a comparative study of the structure and the dynamics of the close packed as well as open surfaces, the calculated shifts in the interlayer spacing, mean square displacement, surface diffusion and surface defects (fissure, dislocation and vacancy) show the onset of anharmonic effects at the characteristic temperatures. Fir the Cu(311) surface interlayer relaxations show a uniform damping in magnitude of oscillatory order (-, +, - , +, . . . ), while for the Cu(210) surface they reveal a non-uniform damping in magnitude with moving away from the surface. The plane registry relaxation at both (311) and (210) surfaces exhibits no order for damping. The diffusion of adatoms on the (111) surface of Ag and Cu has been studied to examine the surface anharmonicity. The diffusion coefficient, effective energy barrier and diffusion prefactor of Cu pentamer on Ag(111) are calculated. The MD simulations at 300, 500 and 700 K show that the diffusivity obeys the Arrhenius Law. An Arrhenius plot of the diffusion coefficients provides an effective energy barrier of 205.25 ±10 meV and a diffusion prefactor 5.549× 1012 Å2/s. A striking feature of a pop-up of single-atom at 700 K among 5-atom island is observed. The effective energy barrier obtained from the xiii Arrhenius plot is in excellent agreement with those extracted from scanning tunneling microscopy experiments. During the diffusion of Cu- and Ag-trimer on Cu- and Ag(111) surfaces at 300, 500 and 700 K temperatures, the constant energy MD simulation are consistent with anharmonic effects at the surface such as fissures, dislocations and vacancy generation in the presence of a island. The fissures and dislocations formed are in the range of 1.5–4 Å and 1–7 Å respectively from the island position. The Cu and Ag islands both diffuse easily on the Cu(111) surface, and indicate that diffusion is faster on the Cu surface as compared to the Ag surface. The process of breaking and opening of the island has been also observed. A surface atom is popped-up at 700 K by generating a vacancy near the Cu island at the Ag surface. The energy of vacancy generation at the Ag surface is found to be Ev = 1.078 eV, in the presence of a Cu trimer. The popped-up Ag adatom combines with Cu the trimer, making a mixed-tetramer (Cu3–Ag island). The adsorption energy of a copper atom from the mixed tetramer island into the substitutional site is Es = ∼– 0.813 eV, leaving a mixed-trimer (Cu2–Ag island) at Ag(111). The rate of diffusion increases with increase in temperature, both for homo and hetero cases. Furthermore, we comment on the effect of adparticles diffusion on the harmonic behavior of the surfaces in the anharmonic regime.
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مقاصد شریعت اور حقوق کی ادائیگی کا باہمی ربط: ایک تحقیقی جائزہ

Allah guided His men through great Prophets and messengers who, through their active economic, religious and politico-economic lives, taught the people how to lead a life. As the people have to come across all these fields of life, therefore, performing rights and duties is essential for a peaceful society. The accomplishment of Sharia objectives depends on the performance of rights and duties. If there is some breach in these rights and duties, the Sharia objectives are lost. If we ponder over the decrees of Allah, it becomes clear that the accomplishment of the decrees itself is the permanence of rights and duties. In this research paper, the rights of the Creator on His men and the rights of men on their Creator, Similarly, the rights of men among themselves and their performance, and the rights of animals and how they can be performed have been described and these Sharia objectives rights are closely related to each other.

Role of Institutions and Policies in Economic Growth: Across Country Analysis

Given the importance of institutions this study tries to find out the relatively unexplored areas on the relationship between institutions, policies and economic growth.As there is extensive literature so far on institutions-growth relationship as well as macroeconomic policies-growth relationship therefore the study contributes by filling the gap on institutions-policies link for developing countries specifically the role of institutions in reducing policy instability. Choice of the countries is based on the governance status or percentile rank of the countries provided by the World Bank, World Governance Indicators. Choice of the time period is relevant to policy initiatives in developing as an agenda of neoliberal approach. Our empirical analysis employs annual data for a set of 12 developing countries, according to the World Bank classification, from South Asia, East Asia and Pacific, Latin America and Sub Saharan Africa.The sample period spans from 1990–2014. 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Results regarding the monetary policy support the Monetarists hypothesis, monetary policy do affect the economic growth through aggregate demand. Trade liberalization increases the economic growth. Liberalizing the capital goods promotes the economic growth through technology transfer. Regarding financial liberalization both the De jure and De facto measure negatively affect the economic growth. Literature provides the evidence that in developing countries financial liberalization increases the risk of crisis, especially due to short run capital flows. Disaggregated analysis shows that FDI inflows positively contribute to economic growth being long term and stable investment while short term investment (portfolio equity and debt) negatively contribute to economic growth due to higher reversal rate. Disaggregated analysis of institutional quality shows that political stability is insignificant in affecting the economic growth while all other indicators of institutional quality positively contribute to economic growth. Rule of law is the most significant factor in affecting the economic growth. xii Regarding our second objective we evaluate the effect of policy instability or volatility on economic growth. We accomplish that volatility of domestic macroeconomic policies brings the uncertainty regarding investment decisions therefore reducing the growth. Volatility of the fiscal policy creates uncertainty about future taxes and the future behavior of fiscal parameters which negatively affects the behavior of economic agents. Volatility of the monetary policy brings volatility in consumption and investment decisions. Access to the external market has destabilized the economies of less developed countries because of volatility associated with trade and capital flows. Volatility of both negatively affects the economic growth by reducing the domestic and foreign investment. Higher integration makes countries vulnerable to external fluctuations that can deteriorate their growth rate. Regarding our third objective we examine the effect of institutions on policy volatility. Results show that institutions play an important role in reducing policy volatility by putting restrictions on policy makers.Regarding the fiscal policy volatility institutional constraints make it difficult for the governments to frequently change the policy. Regarding monetary policy an independent central bank can provide more consistent policy by reducing the uncertainty, in addition to lower inflationary outcome. High institutional quality enables countries to stabilize financial markets and capital flows. Good institutions make the trade flows stable through greater predictability which reduces the trading cost. Besides the institutional quality volatility of domestic macroeconomic policies can be reduced by increasing the level of income, reducing macroeconomic instability indicated by inflation volatility, ensuring the exchange rate stability, higher export diversification, controlling the external debt or reducing the deficit, improving the financial sector development which plays the role of shock absorber in globally integrated world and managing the external shocks. xiii Findings propose that increased globalization has raised the need for transparent, efficient and responsive institutions. To encourage the private investment it is the responsibility of the state to create a suitable legal and economic environment that ensure protection of property rights, strong judiciary and improved transparency. Moreover strong fiscal, monetary and economic institutions reduce policy uncertainty.