【摘要】：本文研究了二維膠體玻璃中玻色峰隨著無序度增加的變化規(guī)律，分析了引起玻色峰的聲子模式的特點(diǎn)，并且探討了聲子模式和體系局域結(jié)構(gòu)的相關(guān)性。樣品是溫敏性的微凝膠，混合直徑大小不同的兩種微凝膠放在兩層蓋玻片中間使其成單層，通過調(diào)節(jié)大小粒子的數(shù)目比來改變體系的無序程度。實(shí)驗(yàn)過程中用視頻顯微鏡拍攝粒子的運(yùn)動(dòng)，拍攝速度是60幀每秒，總共拍攝時(shí)間是11分鐘。拍攝到的視頻用粒子跟蹤技術(shù)得到粒子的位移隨時(shí)間變化的數(shù)據(jù)，接下來用動(dòng)力學(xué)矩陣的方法求解本征頻率和本征矢量。本文關(guān)注二維膠體體系中隨著無序程度的增加玻色峰的變化規(guī)律，所以不同無序程度的樣品的面密度都選取86%。研究發(fā)現(xiàn)隨著體系無序程度的增加態(tài)密度在低頻區(qū)域增強(qiáng)、玻色峰增高。為了研究引起玻色峰的聲子模式的特點(diǎn)，本文計(jì)算了體系中所有振動(dòng)模式的參與比，發(fā)現(xiàn)玻色峰產(chǎn)生的頻率范圍對(duì)應(yīng)的模式是低頻準(zhǔn)局域的。為了研究引起玻色峰的低頻準(zhǔn)局域模式的結(jié)構(gòu)特點(diǎn)，本文計(jì)算了不同頻率下粒子的相對(duì)振幅和局域方向序參數(shù)的關(guān)聯(lián)，發(fā)現(xiàn)低頻準(zhǔn)局域模式與局域無序結(jié)構(gòu)有很強(qiáng)的負(fù)相關(guān)，即低頻準(zhǔn)局域模式往往產(chǎn)生于局域結(jié)構(gòu)無序的位置。接著本文計(jì)算了體系中局域結(jié)構(gòu)（包括自由體積、近鄰數(shù)目和局域熵）的漲落（當(dāng)?shù)亓Ｗ优c其周圍近鄰粒子的結(jié)構(gòu)的差異），同樣也計(jì)算了粒子的相對(duì)振幅與局域結(jié)構(gòu)漲落的關(guān)聯(lián)，，研究發(fā)現(xiàn)局域結(jié)構(gòu)漲落大的位置與低頻準(zhǔn)局域模式有很強(qiáng)的相關(guān)性。所以低頻準(zhǔn)局域模式產(chǎn)生于局域結(jié)構(gòu)無序的位置和局域結(jié)構(gòu)不均勻的位置。
[Abstract]:In this paper, the variation law of boson peak with the increase of disorder in two-dimensional colloidal glass is studied, the characteristics of phonon mode which causes the boson peak are analyzed, and the correlation between phonon mode and local structure of the system is discussed. The samples are thermo-sensitive microgels. The mixed microgels with different diameters are placed in the middle of the two layers of glass slide to form a monolayer. The disorder degree of the system is changed by adjusting the ratio of the number of particles. During the experiment, the motion of particles was captured with a video microscope. The shooting speed was 60 frames per second, and the total shooting time was 11 minutes. The video recorded by particle tracking technique is used to obtain the data of the displacement of particles with time, and then the eigenfrequency and eigenvector are solved by the method of dynamic matrix. In this paper, we focus on the change of boson peak with the increase of disorder in two-dimensional colloidal system, so the surface density of samples with different degree of disorder is 86%. It is found that the density of states increases in the low frequency region and the boson peak increases with the increase of the disorder degree of the system. In order to study the characteristics of phonon modes which cause the boson peak, the participation ratio of all vibration modes in the system is calculated. It is found that the mode corresponding to the frequency range of the boson peak is low frequency quasi-local. In order to study the structural characteristics of the low-frequency quasi-local mode that causes the boson peak, the correlation between the relative amplitude of particles and the local directional order parameters at different frequencies is calculated. It is found that the low-frequency quasi-local mode has a strong negative correlation with the local disordered structure. That is, the low frequency quasi-local mode often comes from the disordered position of the local structure. Then the local structures (including free volume) in the system are calculated. The fluctuation of the number of nearest neighbors and the local entropy (the difference between the structure of the local particle and the nearby particle) is also calculated, and the correlation between the relative amplitude of the particle and the fluctuation of the local structure is also calculated. It is found that there is a strong correlation between the location of local structure fluctuation and the low frequency quasi-local model. So the low frequency quasi-local mode comes from the disordered position of the local structure and the non-uniform position of the local structure.
【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ171.1;O648.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前2條

1 汪衛(wèi)華;;非晶態(tài)物質(zhì)的本質(zhì)和特性[J];物理學(xué)進(jìn)展;2013年05期

2 韓一龍;;利用膠體研究晶體的熔化和結(jié)晶[J];物理;2013年03期

本文編號(hào)：2261467