Cold fusion is caused by the compression against D2 covalent bond at the expanded tetrahedral site (T site) on the nano-roughness of the metal surface, or by the compression against hydride bond of the element. In case of cold fusion on metal surface, D - can occupy the surface T site by expanding T site, and adjacent D+ join to D - by coulomb attractive force between D+ and D- , and D2 is created at expanded surface T site, thus, D2 is compressed by the lattice atoms of T site and small D2 is created by the electron transition from n=1 to n=0, which is theoretically proved by electron deep orbit (small hydrogen) theory. Above Cold Fusion mechanism is based on the following hypo (1) D + and Dcan coexist in the metal, and (2)D+ join to Dat the surface T site (3) D2 exists at the surface T site, (4) compression stress against D2 in the metal surface T site, and (5) small hydrogen caused by the compression stress against D2 covalent bond to change hydrogen into small hydrogen. Lately (1), (3), (5) have been proved by the experiments. (1) has been theoretically studied and experimentally proved by LENR experimental set-up by Lattice Energy Converter by measuring the ion current. (3) has been proved by Lattice assisted nuclear fusion with laser irradiation which laser can trigger Cold Fusion with the frequency of D2 bond vibration, and neutron scattering experiment showed that D occupies surface T site at the preferentially. (5) has been proved by the experiment showed that compressive stress against vanadium-hydrogen- vanadium(V-H-V) bond can turn hydrogen to be smaller hydrogen, which is the electron orbit transition of hydrogen from n=1 to n=0. Small hydrogen has electron in electron deep orbit of n=0 which orbit is so close to the nucleus and small D2 has very high electron density between d-d, electron of D-D bond can shield the coulomb repulsive force between d-d perfectly and cause fusion. Apart from cold fusion in the metal, we have a several other types of cold fusion based on the bond compression. One is the Compression against hydride bonding to trigger nuclear reaction; Typical reactor is ECAT, and they discussed that Li+H reaction, and I presume that its reaction can be caused by the Li-H bond compression to create the small hydrogen (actually neutron) to trigger nuclear reaction. Because this reactor has no mechanism of bond compression, I propose the conceptualized Reactor with the mechanism of bond compression by the stirring of nano Li-H particle with ultrasonic oscillator to vibrate the nano-particle to collide nano-particles each other, and with the metal plate press the nano-metal particle to compress Li-H bond. Similar mechanism of bond compression is NASALattice Confinement Fusion. Although authors think differently, I presume that gamma-ray assists the Er-D vibration and some of Er-D bond can be compressed by Er-D vibration induced by gamma-ray by thermal diffuse scattering, however the efficiency must be very low due to the fusion of d to Er

Keywords : LENR, Cold fusion, neutron, EDO, Electron Deep Orbit, Coulomb repulsive force shielding, transmutation, nano particle Li hydride, Lattice assisted nuclear fusion, Buffer energy nuclear fusion, E-CAT, Lattice confined Fusion, nano metal particle.